This flourless cake is amazing. It's ready in five minutes and makes the perfect keto breakfast or snack. Add a few chocolate chips or whipped cream, and it becomes an indulgent dessert!
I've been working on this cake for a while now. It's a simple cake with four ingredients, but since nut butters greatly vary in texture, it wasn't that easy to get the ratios right. It took several tries, but I eventually reached perfection - a delicious, gooey, and moist cake with just the right level of sweetness.
Ingredients
See the recipe card for exact measurements. Here are my comments on the ingredients.
- Peanut butter: I use natural creamy peanut butter. I typically use Trader Joe's peanut butter, which contains peanuts and salt.
- Egg: I use large eggs in most of my recipes, including this one.
- Sweetener: I use stevia. You can use a granulated sweetener instead.
- Baking soda: You can replace it with a teaspoon of baking powder (gluten-free if needed).
- Optional: Mix a tablespoon of mini chocolate chips into the batter before microwaving.
Instructions
The detailed instructions and step-by-step photos are included in the recipe card. Here's a quick overview.
Mix the peanut butter and egg in a mug or ramekin until completely incorporated.
Mix in the sweetener and baking soda.
Microwave the cake for 30 seconds. If needed, microwave it for 10 more seconds. Don't overcook it! If you wish, top it with keto whipped cream or chocolate whipped cream before serving.
I just tried this and it turned out fantastic! It's so moist and tasty! I used 3 pumps of skinny girl pumpkin praline syrup instead of the liquid stevia. I'm definitely going to make this often!
Flkitten
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I just tried this and it turned out fantastic! It's so moist and tasty! I used 3 pumps of skinny girl pumpkin praline syrup instead of the liquid stevia. I'm definitely going to make this often!Recipe Tips
Based on my attempts, I have a few pointers for you. The gist is that because this recipe relies on peanut butter and microwave baking, the results will vary depending on what peanut butter you use and your microwave.
- Use a freshly opened jar of natural peanut butter and stir it well. If you opt for a half-used jar, the peanut butter might be too dry.
- I don't add salt because my peanut butter is salted. If your peanut butter contains just peanuts, add a pinch of salt.
- Microwaves vary. I always start with 30 seconds, check the cake, then usually add 10 more seconds. By then, the edges are puffed and the center is still gooey - and that's exactly how I like it.
- You should mix the peanut butter and egg thoroughly until the mixture is completely smooth and uniform. If the batter is very thick and sticky, add a tablespoon of water. This makes mixing much easier. The photo below shows you what the batter should look like - smooth, shiny, and not too sticky.
Recipe FAQs
Yes! I was suspicious, too, when I first started making them. But they do work, and they produce results that are very close to a real cake crumb - tender, fluffy, and sweet. The photo below shows you the beautiful, tender crumb of this cake. 
You have some flexibility here. I have made this cake in several dishes. A small and tall 10-ounce mug, a wide 15-ounce mug, and a 3.5-inch-wide ramekin (as shown in the video and the photos on this page).
They all worked, and there wasn't much of a difference. Except that with the ramekin, I was worried there for a moment that the batter might overflow! But it didn't. You can always place your mug on a microwave-safe plate to catch possible spills.
Yes. You can use natural almond butter. If you do, I recommend adding ¼ teaspoon of almond extract to enhance the flavor.
You can store the cooled leftovers in the fridge for up to 4 days (provided you didn't top the cake with whipped cream). You can leave the cake in the mug and wrap the mug in two layers of cling wrap.
You can also freeze this cake. Let it cool completely on a cooling rack, then wrap the mug with plastic wrap, followed by a layer of foil. Freeze the cake for up to three months. You can defrost it in the microwave after removing the layers of foil and cling wrap.
Recipe Card
Keto Peanut Butter Mug Cake
Video
Ingredients
- ¼ cup natural creamy peanut butter - only ground peanuts and salt
- 1 large egg
- ½ teaspoon stevia glycerite - equals 2 tablespoons of sugar
- ¼ teaspoon baking soda
Instructions
- In a medium mug or a large ramekin, mix the peanut butter and egg until completely incorporated. Check especially on the bottom to make sure there is no peanut butter residue.
- If the batter seems very thick, sticky, and stubborn, add a tablespoon of water and keep mixing until completely smooth.
- Mix in the stevia, then the baking soda. Mix well.
- Microwave the cake for 30 seconds. Check it - if it looks very wet, add 10 more seconds. I usually stop at this point - the edges are puffed and done, but the center is still gooey. That's how I like it!
- Enjoy the cake as is, or top it with a dollop of whipped cream for a truly rich experience.
Notes
- Use a freshly opened jar of natural peanut butter and stir it well. If you use a half-used jar, the peanut butter might be too dry.
- Go by how the mixture looks and feels. It should be smooth, shiny, and not too thick. If it's sticky and difficult to mix, add an extra tablespoon of water.
- I don't add salt because my peanut butter is salted. If your peanut butter contains just peanuts, add a pinch of salt.
- I have made this cake in several dishes. A small and tall 10-ounce mug, a wide 15-ounce mug, and a 3.5-inch-wide ramekin (as shown in the video and the photos on this page). They all worked, and there wasn't much of a difference. Except that with the ramekin, I was worried there for a moment that the batter might overflow! But it didn't. You can always place your mug on a microwave-safe plate to catch possible spills.
- Occasionally, baking soda can cause a reaction in baked goods that results in an ammonia smell. If you're concerned about it happening, use 1 teaspoon of baking powder (gluten-free if needed) instead of baking soda. Make sure the baking powder is fresh and not expired.
- You can store the cooled leftovers in the fridge for up to 4 days (provided you didn't top the cake with whipped cream). You can leave the cake in the mug and wrap the mug in two layers of cling wrap.
- You can also freeze this cake. Let it cool completely on a cooling rack, then wrap the mug with plastic wrap, followed by a layer of foil. Freeze the cake for up to three months. You can defrost it in the microwave after removing the layers of foil and cling wrap.
Nutrition per Serving
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Most recipes are low-carb and gluten-free, but some are not. Recommended and linked products are not guaranteed to be gluten-free. Nutrition info is approximate. Please verify it independently. The carb count excludes non-nutritive sweeteners. Please read these Terms of Use before using any of my recipes.
maria says
Surprised but really good. I used cashew, almond, peanut butter. Thank you!!
Vered DeLeeuw says
You're very welcome, Maria!
Flkitten says
I just tried this and it turned out fantastic! it's so moist and tasty! I used 3 pumps of skinny girl pumpkin praline syrup instead of the liquid stevia. I'm definitely going to make this often!
Vered DeLeeuw says
I'm so glad you enjoyed this mug cake! Thank you for leaving a comment.
MCC says
I use vanilla extract, allulose sweetener and a little swerve brown sugar, a tablespoon of heavy whipping cream for moisture, and mix in a few Reese’s peanut butter morsels.
Vered DeLeeuw says
Sounds great! Thanks for sharing your version.