Keto Steak Marinara
Published August 31, 2020 • Updated March 2, 2026
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I turn leftover steak into this steak marinara freezer meal every time we have extra from dinner. Slice, bag, freeze, and cook it in the Instant Pot or on the stovetop whenever you need a fast keto dinner.
Steak marinara sauce recipe
I started making this steak marinara after a night where I had half a pound of leftover ribeye and zero motivation to cook something new. Five minutes of slicing and bagging, and I had a freezer meal ready for the following week. That was three years ago, and I still make a batch every time we have steak for dinner.
The concept is dead simple. Take your leftover steak (any cut works, though I get the best results with flank and sirloin), slice it thin against the grain, and toss it into a freezer bag with marinara, diced tomatoes, spinach, and Italian seasoning. Seal it flat, freeze it, and you have a keto dinner that goes from freezer to table in under 30 minutes. I keep two or three bags in rotation at all times.
What sets this apart from just reheating leftover steak is the sauce. The marinara breaks down into the meat during pressure cooking, and every slice absorbs that rich, tangy tomato flavor. The spinach wilts to practically nothing, which is exactly why I load the bag with two full cups. You get the nutrition without the bulk. If you like my Instant Pot Swiss Steak, you will love how this comes together the same way.
I have made this both from thawed and from frozen. Thawed is faster (7 minutes on high pressure), but frozen works if you add 1/4 cup of water to the liner so nothing scorches. I learned that the hard way. No pressure cooker? The stovetop method is just as good. Thaw the bag overnight, dump it in a skillet, and heat until the sauce is bubbling. It is the same kind of weeknight dinner as my Keto Philly Cheesesteak, just with an Italian spin.
One thing I picked up from a reader: portion into single-serving bags before you freeze. I used to freeze one giant batch and then hack at a frozen block trying to get one plate out. Smaller bags mean you thaw only what you need for one meal. Same cook time, zero waste.
Pour it over cauliflower rice, hearts of palm noodles, or low carb pasta and it is a full dinner. My husband does not even ask what is in it anymore. He just eats it. If you are looking for more Instant Pot meals like this, my Keto Hamburger Helper is another one I keep in the regular rotation.
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Ingredients
1 lb sliced pre-cooked steak -
1/2 cup onion, diced
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2 cups fresh baby spinach leaves
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2 teaspoons Italian seasoning
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1 teaspoon salt
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1/2 teaspoon pepper
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2 teaspoons garlic paste or 2 cloves garlic, minced
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1 cup low-carb marinara sauce or tomato sauce
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1 cup canned diced tomatoes
Step by Step Instructions
Step by Step Instructions
Pressure cook
To prepare, thaw in the refrigerator the night before. Add all ingredients to the liner of an instant pot. Attach the lid and set the vent to seal. Pressure cook on high for 7 minutes. Release pressure by turning the knob to venting. If cooking from frozen, add 1/4 cup of water to the liner of the instant pot along with the ingredients to prevent the contents from burning.
Nutrition disclaimer
The nutrition information provided is an estimate and is for informational purposes only. I am a Doctor of Pharmacy (Pharm.D.); however, this content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or other qualified health provider before making any lifestyle changes or beginning a new nutrition program.
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Get My Macros + Recipes →Frequently Asked Questions
Can I use raw steak instead of leftover steak?
I have done it both ways. With raw steak, you need to increase the Instant Pot time to about 12-15 minutes on high pressure depending on thickness. I slice it thin (about 1/4 inch) so it cooks evenly. The texture is slightly different since raw steak firms up more during pressure cooking, but the flavor is just as good. My preference is still leftover steak because the pre-cooking gives it a better chew in the finished dish.
Should I portion into individual bags before freezing?
This is something I started doing after a reader mentioned it, and I will never go back to the big-batch method. I portion everything into single-serving freezer bags before they go in the freezer. That way I only thaw what I need for one dinner. Same cook time, no waste, and no hacking at a frozen block with a knife.
Does the spinach disappear into the sauce?
Pretty much, yes. I load in two full cups of fresh baby spinach and it wilts down to almost nothing during cooking. That is actually why I go heavy on it. You get the nutrition without changing the texture or flavor of the dish. If you want even more greens, you could easily add an extra cup and not notice a difference.
What cut of steak works best for this recipe?
I have tested this with ribeye, flank, sirloin, and New York strip. They all work. Flank is my top pick because the thinner slices soak up the marinara better during pressure cooking. A reader confirmed the same thing with leftover flank from taco night. Ribeye is richer but can get a little soft. Sirloin is a solid middle ground if you want something leaner.
Can I add mushrooms or other vegetables?
I have thrown in sliced mushrooms and they basically vanish into the sauce, which is a great trick if someone in your house claims they do not like mushrooms. A reader added them to stretch the recipe to five servings without changing the Instant Pot cook time at all. I would keep additions to things that cook quickly at the same rate: bell peppers, zucchini, or diced onion work well.
How long does this keep in the freezer?
I have pulled bags out after two to three months and they tasted exactly the same as week-old ones. Seal the bag flat with as much air pressed out as possible and it stores well. In the fridge, my leftovers keep for three to four days in an airtight container.
What can I use instead of store-bought marinara sauce?
I keep Rao's on hand most of the time, but when I run out I make a simple sauce from canned crushed tomatoes, dried Italian herbs, a little garlic, and salt. It takes about five minutes on the stove. The key is checking the sugar content on whatever brand you grab. Some jarred sauces sneak in 8-10 grams of sugar per serving, and that adds up fast on keto.
Before keto, Sunday marinara was my whole thing. Made this over cauliflower rice last week and that tomato and garlic smell from the Instant Pot brought everything back. I did not realize how much I had missed it until I was eating it again.
Made this probably six or seven times now. Still get excited when there's leftover steak in the fridge, because it means this is happening. The spinach wilts into the marinara in a way I wasn't expecting to like as much as I do. Only knock is I keep forgetting to thaw it the night before, and rushing it never ends well. When I actually do it right and let the Instant Pot do its thing, it's one of the better weeknight meals I make.
My husband is picky about reheated steak and didn't say a word about this one. Something about the pressure cooker keeps it tender. Saving every leftover steak from now on.
The Instant Pot timing is spot on, the steak came out falling apart tender instead of the chewy texture I was bracing for from reheated leftovers. My one note: a cup of marinara gets thin fast over cauliflower rice, so I'll use 1.5 next time. Otherwise, this is locked in.
Yeah, cauliflower rice drinks it up fast. 1.5 is the right call. I'd go closer to 2 if I'm doing a big portion.
Closer to 2 for bigger portions makes sense. I'll try that next time I double it for company.
I had leftover sirloin from dinner and genuinely wasn't sure it would hold up in the Instant Pot (usually that kind of thing comes out grainy and sad), but I had everything else already and figured worst case I'd just eat it anyway. The steak was fine. More than fine. It softened into the marinara and the spinach cooked down like it had been going for hours. It hadn't. Cold night in February. Exactly what I needed.
Sirloin surprised me too the first time I tried it in there. Something about the pressure just smooths it out. Cold night food.
Tried this with leftover flank steak from taco night and it worked so much better than I expected. The thinner slices soaked up the marinara in the Instant Pot and I honestly could not believe how fast this came together. I also threw mushrooms in to stretch it to five servings and they basically disappeared into the sauce, so if you're picky about vegetables, this is a good trick. One thing I figured out: portion it into smaller freezer bags before you freeze so you're only thawing what you need for one serving. Same cook time, no waste, no sad leftover sauce sitting in the fridge. The house smelled incredible while it was cooking and I am genuinely annoyed I did not make a double batch.
Never thought to portion before freezing but that's what I should be doing. I'm always hacking at a frozen block trying to get one serving out. Double batch next time, this keeps for 2-3 months in there.
Husband said it was better than his usual protein bowl. Spinach cooks down perfect in the instant pot
The spinach wilts down to basically nothing in there, right? I go heavy on it for that reason.