Kirbie's Cravings

3 Ingredient Keto Peanut Butter Mug Cake

A single serving microwave peanut butter mug cake that is only three ingredients. It’s quick, easy and is also keto-friendly, low carb, wheat flour free, and gluten free.

I’m on a quest to make more keto-friendly mug cakes. First up, this peanut butter mug cake. All you need is natural peanut butter, egg and a sugar substitute. That’s it! If you want a full-size cake you should definitely check out my 3-Ingredient Keto Peanut Butter Cake.

Texture of the Mug Cake

This cake is based on my flourless peanut butter mug cake so the cake has a flourless souffle-like texture. It is not supposed to have a texture like a flour-based cake. It is soft, fluffy and rises quite a bit. To get a little more height and fluff, you can add a little baking powder.

Type of Peanut Butter to Use

I recommend using natural creamy unsalted peanut butter. There are a lot of peanut butter choices out there these days. But they are not all the same. I always look at the ingredient list and buy ones that list peanuts as the only ingredient. No extra oils, sugar, etc.

Type of Mug to Use

This cake will rise quite high during cooking before sinking back down. You should use a microwave-safe mug that can hold at least 12 oz of liquid. You can use an even larger mug, but if you want the cake to rise to the top, it will just fill a 12 oz mug.

Topping Ideas

You can top the cake with a little powdered sugar substitute or sugar-free syrup. Or you can also top it with a simple peanut butter sauce.

For my peanut butter sauce, I warmed up 1 tbsp of peanut butter in the microwave and whisked in a little milk (1 tsp at a time) until it reached a thick syrup consistency. I also mixed in a little stevia until it reached my desired sweetness. I then poured the peanut butter sauce over the cake (I did not use the full amount).

More Keto Cake Recipes

photo of a keto peanut butter mug cake

3 Ingredient Keto Peanut Butter Mug Cake

Course: Dessert
Cuisine: American
This easy microwave mug cake is just 3 ingredients! It's so quick, easy and is also keto and low carb.
4.63 from 16 votes


  • 2 1/2 tbsp natural creamy unsalted peanut butter
  • 2 1/2 tsp Natural Mate All Purpose Granular Stevia or sugar substitute of your choice equivalent to 1 tbsp + 2 tsp sugar
  • 1 large egg


  • In a microwave-safe mug that can hold at least 12 oz of liquid, add all ingredients. Mix with a whisk until batter is completely smooth and egg is fully incorporated with no egg streaks remaining. Your batter should look like melted peanut butter.
  • Cook in the microwave at full power for about 1 minute. I used a 1000 watt microwave. You may need to adjust cooking time and power if your microwave is a different wattage. Cake is best enjoyed warm.


  • To make the mug cake even fluffier, add 1/8 tsp baking powder to the batter. I don't recommend adding more than 1/8 tsp because it will make the cake rise too much and dry out the cake.
  • For the sugar substitute, I used Natural Mate Stevia All Purpose Natural Sweetener*
  • If you have a favorite keto friendly sugar substitute, it will likely work with this recipe. Just make sure you add the equivalent of 1 tbsp + 2 tsp of sugar.
  • If you like your cake a little sweeter, you can add a little more sugar (up to 1 tbsp stevia or 2 tbsp sugar substitute equivalent), but your cake will not rise as much.
  • The cake is best consumed warm. If you are not consuming it right away, make sure to keep it covered or in a sealed container because it can get dry quickly if it's just left unsealed.
  • The batter needs to be well-mixed. If you have streaks of egg whites not mixed in, your cake will not cook properly.
  • I use a 1000 watt microwave. If your microwave power is less or more, please adjust cooking time and/or cooking power accordingly.
  • *Some of the product links contained in this post are affiliate links. Much like referral codes, this means I earn a small commission if you purchase a product I referred (at no extra charge to you).
Estimated Nutrition Information does not include toppings or carbs from erythritol.


Serving: 1cake, Calories: 318kcal, Carbohydrates: 9g, Protein: 15g, Fat: 25g, Saturated Fat: 4g, Sodium: 80mg, Fiber: 3g, Sugar: 1g, NET CARBS: 6

The nutrition information provided are only estimates based on an online nutritional calculator. I am not a certified nutritionist. Please consult a professional nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.

Did you make this recipe?I'd love to see it! Mention @KirbieCravings and tag #kirbiecravings!


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Recipe Rating

71 comments on “3 Ingredient Keto Peanut Butter Mug Cake”

  1. Very good and some easy preparation

  2. I’ve made it it was abit dry maybe I’ve over cooked it a bit but it was nice I will try it again

  3. I made this for my better half as she is on a low-carb diet. She and I both loved it.

  4. So good! I used an erythritol and Allulose mix for the 1 tablespoon and 2 tsp of cane sugar as the sweetener. I added a little less than a tablespoon of 100% cacao chips. Topped with the sauce, I used peanut butter and a big pinch of erythritol/Allulose mix and about a teaspoon of unsweetened vanilla almond milk (30 cal per cup). This is so good and delicious and easy!

    We just switched to low carb (not keto) for our 7 year old who was just diagnosed with type 1 diabetes to keep his blood sugar swings under control. I know he feels like he doesn’t get goodies like we used to. And he’s also allergic to dairy and soy, which makes things more restrictive (and expensive!). This was the delicious pick-me-up we all needed. Plus we travel full time and using a propane oven is not always very fun – microwave was perfect. Thanks for delicious, easy recipes!

  5. I didn’t have peanut butter on hand but had pb2 powder so I decided to experiment a bit. Made the peanut butter with mater with the pb powder then followed your instructions. It was pretty good actually. I did add the baking powder because I like mine a bit on the drier end but as it turns out 1/4tsp didn’t dry it out at all. It turned out pretty moist. Thanks for this recipe. 

  6. I just skip the sugar / substitute all together. Doesn’t make a difference at all.

    The compound at the end I find is really dry (like almost eating bread so no biggy) so I just add some 95% less sugar (natvia) jam and it’s perfect for Keto.

  7. Hi, Jennifer. Today I made 3 INGREDIENT KETO PEANUT BUTTER MUG CAKE and added slices of banana. It tested very delicious, mouthwatering, and heavenly. I enjoyed it very much ?. Your recipe is exquisite ?.

  8. This Mug cake looks and sounds so yummy,but Yikes! so any cal’s. No doubt it all comes from the PB. Please let me know if I can use the equivalent of PB2 – powdered PB? I am looking everywhere for mug cakes/muffins and I barely find anything, or too many ingredients hence the calories. So I’m trying to lighten this,too.

  9. What’s is the topping on the mug cake in the pic? Thanks! 

  10. Do you have baking suggestions ILO microwave?

  11. I don’t understand the logistics of why this would work so was hesitant to try it.
    Today was cold and windy so I made it. So well worth it. Very creamy, smooth and delicious. I didn’t even need a topping for it.

  12. Question, can you use a powdered peanut butter?

  13. Really easy, lovely & just right for that late night craving when I realised I needed a protein hit that was sweet.
    I’m on day 3 of a restart and although I didn’t want to be hitting the sweet subs already this was needed! It’s 2am in the UK and I was hungry!
    Topped off with a smidge of 80% dark chocolate melted in some double cream ? I’m not counting calories yet just trying to purge the carb reliance out my system.
    Thank you thank you thank you ?

  14. Can’t wait to try this, have to get all natural peanut butter. Thank you for recipe. Maybe I can stick to program with recipes like this!!

  15. What can I substitute for the egg? A friend of mine is allergic 

  16. So good and so quick and easy!

  17. What is the liquidy topping on the mug cake?

  18. Follow the recipe exactly and it turned out perfect! I enjoyed it with coconut whipped cream. Delicious!!
    Thanks for the recipe!

  19. All I can say is WOW. The PB mug cake. Made me do a happy dance. Topped mine with some unsweetened strawberry preserves. Put a little squirt of lemon juice. All I can say is that my tummy says thank you…

  20. I don’t have a microwave. Can I use an oven to do this instead? 

  21. This is so so so good! Not eggy at all – just delicious peanut butter and I added a sprinkle of Lilly’s chips after it came out of the microwave. It feels like I’m cheating 🙂

  22. This is an awesome recipe. I’m always searching for good low carb recipes for when my sweet tooth kicks in. The only thing I I did differently was add a little bit of honey. The texture was great, and it wasn’t too eggy like most mug cake recipes tend to be. Thanks so much!

  23. Oh my this was like a slice of Heaven!!  I threw in some Lily’s chocolate chips and topped it with a sugar free caramel sauce and a spray of whipped cream!!  I’m making this again!!  Thanks for sharing it!!??

  24. What a delicious treat! I used chunky peanut butter and sf chocolate chips on top. The consistency and the taste were both spot on. The best thing was how easy it was to make. Thanks!

  25. I don’t usually comment on recipes but wow! The texture of this is so much better than most keto mug cakes and it tastes awesome. I wish I had some chocolate on hand to go in it as well. This will be on my rotation for sure

  26. how big of a cake does this make?

  27. Has anyone tried this with almond or macadamia nut butter?

  28. Hmm tempted to try with the chunky peanut butter I have ?

  29. Wow. This tastes even better than mug cakes that call for almond or coconut flour and the texure was so fluffy and satisfying. Thank you so much for the recipe! Delicious. 

  30. This is BY FAR the best and easiest mug cake I’ve ever made. It’s so delicious, I added a little bit of lilly’s Chocolate chips and a touch of baking powder. It was so delicious and moist, I don’t even know how it was as good as it is. Amazing. 

  31. Can I use honey as a sweetener? 

  32. You didn’t say to butter the inside of the mug?????