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Stained Glass Cake

Annie Lampella, Pharm.D. Recipe developer and pharmacist

Published Updated

18 ratings

Colorful 'broken glass' cubes float in this stained glass cake's creamy vanilla base — a no-bake, sugar-free slice of art at just 0.2g net carbs and 16 calories. My trick: agar instead of gelatin.
  • 0.2gnet carbs
  • 1.3gprotein
  • 35minutes
  • 8servings
A wedge of layered stained glass cake topped with whipped cream and a strawberry slice.
Three slices of stained glass cake topped with whipped cream and strawberries.
Black springform pan filled with red, green, and translucent gelatin cubes.
A slice of stained glass cake being lifted from a full cake, showing colorful layers.
Strawberry-topped stained glass cake slice on a white plate with more slices in the background.
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I originally made this as my keto version of the classic broken glass Jello cake, but I didn't use Jello here (save that for my Jello whip recipe). Instead, I used agar agar powder, which gives that same gelatin-like set without the sugar, carbs, or animal products. If you've made my raindrop cakes before, this is a similar concept, just with a lot more color and flair. I wanted a dessert that looked impressive but stayed completely clean on macros, and this is what I came up with.

Close-up of three vibrant stained glass cake slices showing clear layers of gelatin and cream.

The colored cubes are made with water, agar, and a powdered sugar-free sweetener. Once set and cut, they get layered over a creamy vanilla base (also agar and heavy cream) to create that broken prism effect. A final clear agar pour seals everything so it slices cleanly into wedges or squares. I use a 6-inch springform pan because the taller cross-section really shows off the color pattern. Each piece looks completely different depending on where the cubes landed.

I've made this at least a dozen times now, and the thing I keep coming back to is how agar works better than gelatin here. Agar sets at room temperature in about 15 minutes, no waiting around for hours with your fingers crossed. The cubes hold their shape when you slice, and the whole thing stays firm even sitting out at a party for a couple hours. Gelatin would go soft and saggy in that same situation. If you like my keto panna cotta, you'll recognize that same clean, smooth set that agar gives you.

The whole dessert is no-bake, zero-carb, and basically zero calorie, which makes it perfect for warm weather when I don't want the oven on. I've brought this to summer get-togethers and holiday parties, and people genuinely don't believe it's low-carb. It looks too fancy for something that takes 30 minutes of active work and zero baking. For holidays, I swap the food coloring to match (red and green for Christmas, red and blue for July 4th). For more no-bake ideas, try my keto cheesecake fluff or raspberry no-bake cheesecake.

The first time I sliced into this, I just stared at it. Every piece had a different pattern of color cubes running through it, like looking through a kaleidoscope. You don't need any decorating skills for that. No piping, no fondant, no tempering. You pour, chill, and slice, and the art happens inside the cake on its own.

Three triangular slices of stained glass cake with strawberries on a white tray and purple background.

Why I use agar instead of gelatin

I’ve tested both, and they’re not interchangeable. Agar comes from seaweed, sets firm at room temperature, and holds its shape when you cut it. Gelatin comes from animal collagen, needs hours in the fridge, and gives you a softer, jigglier result. For this recipe, agar is the better choice because the cubes stay crisp and defined when you slice through the cake. If you prefer working with gelatin, try my keto gummy worms where that softer set actually works in your favor. Agar is also vegan and keeps the whole dessert in keto territory with zero carbs.

How to store it

I keep mine in the refrigerator and it stays fresh for 3-4 days. You don’t need to cover it unless you’re storing it next to something with a strong smell (onions, garlic, that kind of thing). The agar holds its texture in the fridge without breaking down, which is one of the reasons I prefer it over gelatin for make-ahead desserts. If you’re prepping for a party, I make the cubes and cream base a day or two out, then do the final assembly and clear seal the morning of.

Tips for working with agar

The biggest thing to know about agar is that it sets at room temperature, fast. Once your colored mixture comes off the heat, you have maybe 10-15 minutes before it starts firming up. I pour into bowls and add food coloring right away. If you try to do it slowly, you'll end up with uneven distribution in your finished slices. Have your bowls, food coloring, and extracts all ready before you start heating. If the mixture starts getting thick in the pan, put it back on low heat for 30 seconds to re-melt.

For colors that actually taste like something, match your extracts to your colors: raspberry for red, lemon for yellow, and leave the third batch clear with vanilla. Agar has zero flavor on its own, so without the extract you're just eating pretty shapes. I've also done orange extract with orange coloring for a fall version, and peppermint with green for Christmas.

You can make the colored cubes and cream base up to 2 days ahead. Keep them covered in the fridge, then assemble and pour the clear seal when you're ready. I do this for parties so the day-of work takes about 10 minutes. If you like colorful no-bake projects, my bomb pops have a similar vibe in popsicle form.

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The recipe

Stained Glass Cake

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Prep 20 min Cook 15 min Total 35 min Serves 8

Ingredients

Servings 8

Stained Glass Cake Ingredients

Step by Step Instructions

  1. Make agar solution

    Combine 2/3 cup water, 1 ¼ teaspoons agar powder and 1/4 cup powdered sugar-free sweetener into a small saucepan. Heat over medium high heat until boiling. Remove from heat.

    For this step

    • 2/3 cup water
    • 1 ¼ teaspoons agar powder
    • 1/4 cup powdered sugar-free sweetener
    A saucepan of agar agar mixture being heated on the stovetop until dissolved.

  2. Cream base

    Stir in nut milk or heavy cream into the agar mixture. Pour into a parchment lined 6 inch springform pan and refrigerate for 30 minutes or until set.

    For this step

    • 1 ⅓ cup nut milk or heavy cream
    The creamy white agar base layer being poured into a springform pan.

  3. Make more agar solution

    In a clean saucepan, combine 1 ⅓ cup water, 2 ½ teaspoons agar powder and 1/2 cup powdered sugar-free sweetener. Heat over medium high heat until boiling. Remove from heat.

    For this step

    • 1 ⅓ cup water
    • 2 ½ teaspoons agar powder
    • 1/2 cup powdered sugar-free sweetener
    A second batch of agar agar being heated to create the clear gelatin layer.

  4. Make the stained glass

    Stir in vanilla extract and 1 ⅓ cup water. Separate mixture equally into three bowls. Add two different colors of food coloring to only two bowls and mix to combine. Pour each bowl into a small baking dish or plastic container. Refrigerate for 30 minutes or until set.

    For this step

    • 1 teaspoon vanilla extract
    • 1 ⅓ cup water
    Three containers filled with green, clear, and red colored agar gelatin cooling to set.

  5. Layering the stained glass

    Once hardened, cut the three colored mixtures into small squares and place on top of the cream layer, alternating the colors as you cover the entire surface.

    Cubes of red, green, and clear gelatin scattered on top of the set white layer in the pan.

  6. Seal the cake

    To create an even cake and to help seal the layers together, prepare one final mixture of agar solution. Heat 1/3 cup water and 1 ¼ teaspoon agar powder in a saucepan until boiling. Remove from heat, add in 1 cup water. Let cool for a couple of minutes. Pour agar mixture over the cake until it covers the entire cake. Refrigerate for 30 minutes or until set.

    For this step

    • 1/3 cup water
    • 1 ¼ teaspoon agar powder
    • 1 cup water
    Clear liquid agar mixture being poured over the colored cubes to form the top layer of the cake.

Nutrition

Per serving: 1 slice

Calories
16
Fat
0.5g
Protein
1.3g
Total carbs
2.5g
Net carbs
0.2g

Nutrition is an estimate calculated from the ingredients listed. Brands vary, so check labels if you track closely.

Frequently Asked Questions

Can I use gelatin instead of agar agar powder?

I've tried both, and they're different experiences. Gelatin sets softer, needs hours in the fridge, and the cubes come out jigglier. Agar sets firm at room temperature in about 15 minutes, and the cubes hold their edges when you slice. If you go with gelatin, you'll need roughly 3 times the amount by weight to get similar firmness, and the whole recipe takes much longer. I prefer agar here because the cubes stay crisp and the slices look clean. The result also won't be vegan or as low-carb as the original.

Can I use different flavors and colors?

I mix and match all the time. My go-to is raspberry extract for red, lemon for yellow, and plain vanilla for the clear batch. Agar has zero flavor on its own, so without extract you're just eating colored shapes. I've also used orange extract with orange coloring for a fall version, and peppermint with green for Christmas. Pick flavors you actually want to taste and match the colors to them. You can also use sugar-free drink mixes or flavored water if you don't have extracts on hand.

How far in advance can I make this?

I prep the colored cubes and the cream base layer up to 2 days ahead. They keep their shape in the fridge with no issues. Then on the day I'm serving, I assemble the cubes on the cream base and pour the clear seal, which takes about 10 minutes. The fully assembled cake lasts 3-4 days in the fridge, so you could also make the whole thing the day before and it'll hold up perfectly.

Can I make this dairy-free?

I've made this with full-fat coconut cream instead of heavy cream for the base layer, and it works well. The coconut adds a slight flavor that I actually like with the fruit extracts. Use canned coconut cream (the thick stuff), not the carton coconut milk, or your base won't set firm enough. With coconut cream and agar, the whole dessert is fully vegan too. If you like coconut-based keto desserts, my dairy free ice cream uses a similar swap.

Why did my agar start setting before I finished pouring?

This is the most common issue I hear about, and it happened to me the first time too. Agar sets at room temperature, so it starts firming up the second it comes off the heat. I've learned to have my bowls, food coloring, and extracts all ready before I even start heating. Once it's off the stove, I pour into bowls and stir in color immediately. The whole pour-and-color process should take under 2 minutes. If you notice it getting thick in the saucepan, put it back on low heat for 30 seconds to re-melt.

Can I double this for a larger pan?

I've doubled it using a 9-inch springform pan and it works, but the slices won't be as tall so the prism effect is less dramatic. If you want that tall, impressive cross-section, I'd make two separate 6-inch cakes instead of one big one. The proportions stay the same either way. I've also made half batches in a small loaf pan for just my husband and me, and that works fine too.

Is this vegan?

The agar version is plant-based since agar comes from seaweed. If you also swap the heavy cream for full-fat coconut cream in the base layer, the whole thing is completely vegan. I've done this a few times for friends who are dairy-free and they couldn't tell the difference in texture. The set is the same, and the coconut flavor is subtle enough that it doesn't take over.

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Reviews

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4.8 from 18 ratings, 14 written

Made this recipe?

Replying to Mark

Your rating

LuAnn T.

I have a birthday coming up and I’m making this one. The agar squares hold their shape so well! 😂

Reply

Roberta

I have gelatin in the cupboard but no agar and I don’t want to wait on an order. Will the cubes still hold their shape if I swap it, or is the agar doing something gelatin can’t?

Reply

Frank

Whip the cream base a little before it sets and you get a softer bite against the cubes. I honestly thought agar would be a downgrade from gelatin, way too stiff, and I almost bought gelatin instead. Nope, it holds the squares in place better and the slices stay clean. Way better than the gelatin version I made last year!!

Reply

Annie Lampella

Thank you Frank! I haven’t whipped the base before it sets. I’m trying that next time.

Reply

Sam I.

Assumed it would look nothing like the photo. Got the springform off and the cubes are exactly where they’re supposed to be. 16 calories. Still processing that.

Reply

Annie Lampella

I always run a thin knife around the edge before I unclip the springform, Sam, makes it so much cleaner.

Reply

Greg

Give yourself more time to chill the layers than you think you need. I rushed it and the cubes started drifting when I poured the vanilla base over, but it still came out looking incredible. Two years of keto and I had honestly stopped expecting desserts to look like anything worth photographing, so unmolding this was a lot.

Reply

Annie Lampella

The drift happens fast. If the cubes aren’t fully cold through the center, warm vanilla base softens the outer edges just enough to shift. I give mine at least 3 hours, overnight in summer. Two years and that unmold still gets you, Greg.

Reply

Lorraine

Month three of keto I basically wrote off desserts that looked like real desserts. Unmolded this last night and just stood there, the agar squares suspended in the vanilla base looked exactly like something I’d pay for. 0.2g net carbs and I’m still not over it.

Reply

Brett

Added a drop of raspberry extract to the red layer and a little lime juice to the green, just to see. When the color and flavor actually match it feels intentional, like you meant it instead of just making it look pretty. Subtle, but it makes a difference. Doing this every time now.

Reply

Annie Lampella

Raspberry for red is exactly what I do. The lime for green I hadn’t tried (I usually go lemon for yellow), but lime makes more sense visually. Might steal that.

Reply

Jordan

Making this for a birthday dinner Saturday. Can the whole thing be assembled and refrigerated overnight, or do the agar layers need to stay separate until closer to serving?

Reply

Annie Lampella

Both parts are fine 2 days ahead, refrigerated separately. Day-of assembly keeps the cross-section sharp when you slice.

Reply

Hannah

Made this over the weekend and the agar pieces came out really firm, almost rubbery. Not sure if I used too much agar or if that’s just how it is compared to gelatin. Do they soften once set in the cream, or should I scale back next time?

Reply

Annie Lampella

Agar is just firmer than gelatin, so some of that is normal. If it felt rubbery though, scale back to 3/4 teaspoon per color batch. They won’t soften up once they hit the cream.

Reply

Chris

Swapped in full-fat coconut milk for the nut milk and the base set way firmer. Cubes stayed put when I sliced it instead of sliding around. Worth it if you care how it looks.

Reply

Annie Lampella

Coconut milk runs way higher fat than most nut milks so that tracks. Coconut cream is even denser if you want max hold on the base.

Reply

Lauren Z.

Never bought agar before and spent an embarrassing amount of time in the store staring at the package. It worked though. When I sliced it and saw those colored squares suspended in the white base, I genuinely didn’t believe I’d made it myself.

Reply

Annie Lampella

That first slice is the whole payoff. Agar shows up in different spots depending on the store, usually Asian foods or baking, sometimes near supplements.

Reply

Renee

Made a full batch Sunday night and I keep opening the fridge just to look at it before actually eating any. The colored agar squares look almost too good to cut, but every slice comes out clean. Four days in and the texture is the same as day one. Exactly the make-ahead dessert I’ve been looking for.

Reply

Annie Lampella

I still hesitate before the first slice every time. Agar locks that texture in for days.

Reply

Alex

Making this for Easter. I tracked down agar at my grocery store, but it only came in strip form, not powder. I’ve seen the 3x-by-weight rule but wasn’t sure if it applies to no-bake recipes. Would strips work if I adjust the amount, or does the texture really depend on using powder?

Reply

Annie Lampella

Strips work. Triple the weight and give them more time on the heat, they’re slower to dissolve than powder. Check for any bits still floating before you pour.

Reply

Mark

My grandmother used to make a jello mold version of this every Christmas and I thought those colorful desserts were just behind me on keto. That vanilla cream base with the colored cubes looks exactly like what I remember sitting on her counter as a kid, and for basically zero carbs. Easter is going to be so good.

Reply

Annie Lampella

Easter is perfect for this. I’d do pink, lavender, and yellow for the cubes, soft pastels against that white cream base are going to look exactly right on the table.

Reply

Wendy

Warm your knife under hot water before cutting the colored agar pieces and the edges come out SO sharp they actually look like real stained glass instead of just random blobs.

Reply

Annie Lampella

Cold blade drags through the agar and you lose the edge. Run mine under the tap now before every cut.

Reply

Sarah

Served this Saturday and two guests were already Googling bakeries before I admitted it was agar powder and 16 calories a slice.

Reply

Annie Lampella

Ha, the pre-reveal bakery search. That’s the best version of the compliment.

Reply

Dana

The presentation on this is honestly beautiful, and mine came out looking almost exactly like the photos, which almost never happens for me with fancy no-bake projects. The agar was more temperature-sensitive than I expected though, and that’s where I ran into trouble. My colored pieces started setting before I finished pouring them into separate bowls, so the distribution in my final slice was a little uneven compared to what I was going for. The cream base is lighter than you’d expect for something with zero sugar. Four stars because the concept is perfect and the flavor is there, but a note about working fast once the colored agar comes off the heat would have saved me a lot of scrambling. Next time I’m doing smaller batches so I can stay ahead of it.

Reply

Annie Lampella

Smaller batches, yes. Have every bowl sitting right there before the agar even comes off the heat. You get maybe 90 seconds before it starts grabbing.

Reply

Christine

Matched the extracts to the colors (raspberry for red, lemon for yellow) and it finally made sense. Agar is so neutral that without them you’re just eating pretty shapes.

Reply

Annie Lampella

Raspberry for red, lemon for yellow is exactly what I do. Agar has zero flavor by itself, so without extract you’ve got nothing but color.

Reply

Elaine

Do I need to use agar powder specifically or would gelatin work the same way? I’ve never used agar before and not sure if it’s worth ordering online or if I can just grab gelatin at the grocery store.

Reply

Annie Lampella

You can use gelatin but it sets softer and takes longer to firm up. Agar sets at room temp in like 15 minutes, gelatin needs fridge time. The cubes won’t be as firm either, more jiggly. I like agar for this one because the cubes hold their shape when you slice it.

Reply

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