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.
4.5 from 10 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, Potassium: 337mg, Fiber: 3g, Sugar: 1g, NET CARBS: 6g

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

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

  2. Do you have baking suggestions ILO microwave?

  3. 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.

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

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