Keto Strawberry Rhubarb Upside Down Cake

I have rhubarb in the fridge from the farm stand and book club is Thursday, so this is happening! Fingers crossed it comes out of the pan in one piece!

Most almond flour cakes go heavy the second they cool. Not this one, something about the coconut flour ratio. Caramel ends up the actual star, and the rhubarb tang comes through instead of disappearing under sweetener like usual.

Grease the bundt pan like you actually mean it because the caramel will find any spot you skimped on, ask me how I know. I went in expecting the almond flour sponge to do what most keto cakes do for me, which is taste pretty close but leave this small reminder that something’s off, and I kept waiting for that while I was eating it and it just never came. The rhubarb gets so jammy against the monk fruit that I found myself comparing it to the non-keto upside-down cake I used to make, and honestly it held its own. I’m not usually one to rave about a keto dessert but I’ve already looked up if you can freeze rhubarb.

5.4 net carbs seemed really low for a fruit dessert so I double-checked the math. But the bigger thing: pan prep. Clarified butter brushed into every groove of the bundt instead of spray, and the fruit layer came out in one clean piece, nothing tearing. Also cut the erythritol in the fruit topping by half and subbed coconut sugar (adds a carb or so per slice) and the caramel came out richer in color. Worth it if you want that more lacquered look on the flip.

Annie, do you have any tips for how many ounces by weight the rhubarb should be? I’ve only ever seen or used rhubarb from my garden and the stalks can be like 2.5 feet long.

I’m making rhubarb crumble today and accidentally picked 2 lbs more than needed so have some extra to go in the freezer!

I’m really excited to make your cake, especially since you say frozen rhubarb works best. Rhubarb is so good and it took a couple of years but now I’ve developed an amazing low carb rhubarb crumble recipe. I make custard to pour on top and it’s my favorite dessert!

Four batches in and the caramelized fruit layer sliding out of the pan clean still makes me unreasonably happy.

The flip actually worked, which I did not expect as someone who has never made a bundt cake before. Came out clean and the caramelized fruit layer looked like the photo. My one note is that the rhubarb is sharper than I anticipated. If you’re expecting something sweet-forward, the tartness catches you off guard. I think I’d reduce it by one stalk next time and let the strawberry carry more of the flavor. Still made the whole thing disappear by Sunday evening.

So I couldn’t find fresh rhubarb anywhere (it’s early for my area) and just used frozen, fully expecting to ruin this. Thawed and drained it really well first since I read that frozen fruit releases more liquid, and the arrowroot powder still held everything together when I did the flip. The caramel layer came off the bundt pan clean, like actually clean, and I genuinely stood there staring at it for a second. I also threw in an extra half teaspoon of lemon zest because I wanted more tartness, and it made the whole thing sing in a way I didn’t anticipate. For someone who has never made an upside down cake and is still pretty shaky on keto baking, this felt freaking unbelievable. I’m doing it again with fresh rhubarb the second it shows up at the market because I need to know how different it actually is.

Strawberry rhubarb was my grandma’s thing, then mine, and I figured keto killed it. Found rhubarb at the farmers market last week and made this. When I flipped the bundt pan and that caramelized layer came out clean, I actually gasped. Felt like something I’d written off coming back. It’s denser than a traditional upside-down cake (almond flour does that), but not in a bad way. Making it again before the season’s gone.

I batch bake every Sunday and this went into the rotation three weeks ago because I needed a dessert that would actually survive four days in the fridge without falling apart. Didn’t expect this: the caramelized strawberry rhubarb layer gets almost jammy overnight, way better than fresh out of the oven. I’ve been slicing it the morning after baking, wrapping individual pieces in parchment, pulling them out all week. Hard-learned tip after destroying two slices: chill the whole bundt before you cut into it, or the caramel layer tears instead of separating clean. I’m a total beginner and this is now the fanciest thing I make, I freaking love flipping that pan every time. Double batch next Sunday for sure.

My daughter made me promise not to tell her what rhubarb was until she finished her slice. Honestly, that made the slightly sticky bundt release worth it.

The flip is terrifying when you’ve never made an upside-down cake before. Mine came out cleaner than I expected (the caramelized fruit layer just slid right out of the bundt pan), and now I’m wondering if the arrowroot powder is what keeps it from sticking. Is that what it’s doing, or is it more for the fruit texture?

The flipping part is what’s making me nervous about trying this. Is there a way to tell when it’s ready to come out of the bundt pan cleanly, or do you just go strictly by the bake time? I’d hate to lose that whole caramelized fruit layer to the pan.

Taste and texture are there, but mine needed closer to a full teaspoon more sweetener in the fruit layer. Rhubarb is pretty tart and the recipe amount left it sharper than I expected. Worth adjusting before you commit to the flip.

I’ve made basically every keto dessert and had real doubts about rhubarb, it always goes so sour on me even in regular baking. Had some sitting in the fridge and just went for it. That moment when you flip the bundt pan and the caramelized fruit comes out clean in one piece, I genuinely didn’t expect it to look that good. The golden monk fruit does something to the rhubarb, no tartness at all, just this jammy layer that beats anything else I’ve tried on keto.

Grabbed frozen rhubarb because fresh wasn’t happening in February and it caramelized into this thick jammy layer at the bottom of the bundt (way more concentrated than I expected), not using fresh for this one ever.

Annie, thanks for a delicious recipe! I made it for my husband’s 71st birthday & he loved it! I flubbed by adding the reserved sweetened butter to the batter (pro tip: don’t sit the sour cream & butter side-by-side). I went ahead & put in the sour cream too, praying it would turn out ok & mixed up more sweetened butter. It baked in 45 min, cooled in the pan for 30 min. When I flipped it over, only a few pieces of topping were left behind in the pan. Yum!

Can I use softened solid coconut oil instead of butter?

I have made this twice and it is absolutely delicious. However both times I have cooled the cake for a min of 45 minutes to an hour. Each time I have had the issue of the fruit/veg (I used the 1 tsp xanthan gum swap) top sticking and staying in the bundt pan, the first time taking a piece of the cake too as I flipped it. I liberally sprayed the pan with coconut oil before baking, and the second I also used some butter with no difference. Any tips or idea’s as to why this is happening? If it’s for me I don’t mind, but this is for a family member that cannot eat the traditional pineapple upside down, so I would like to present it as perfectly as possible.
Thanks,
Mel