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
3 Ingredient Keto Peanut Butter Mug Cake
Ingredients
- 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
Instructions
- 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.
Notes
- 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).
Nutrition
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.
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I made this for my better half as she is on a low-carb diet. She and I both loved it.
We’re glad you both loved it!
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!
Thank you for your nice comment! We’re so glad you loved the recipe.
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.Â
Peanut powder was mixed with *water to make a peanut butter like mixture.Â
Thanks for sharing your adjustments! We’re glad it worked for you.
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.
Thanks for sharing that!
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 ?.
Thanks so much!
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.
Sorry, but we haven’t tried it with powdered peanut butter.
What’s is the topping on the mug cake in the pic? Thanks!Â
All of the information is listed under the “Topping Ideas” section in the post.
Do you have baking suggestions ILO microwave?
You might like our single-serving Baked Keto Peanut Butter Cake.
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.
i”m glad you liked it!
Question, can you use a powdered peanut butter?
Sorry, we haven’t tried this recipe with powdered peanut butter.
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 ?
I’m so glad it worked out well for you!
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!!
I hope you enjoy!
What can I substitute for the egg? A friend of mine is allergicÂ
Sorry I do not have an egg substitute for this recipe.
So good and so quick and easy!
I’m so glad you liked it!
What is the liquidy topping on the mug cake?
it’s a peanut butter sauce which I discuss in the post along with how to make it
Follow the recipe exactly and it turned out perfect! I enjoyed it with coconut whipped cream. Delicious!!
Thanks for the recipe!
I’m so glad you liked it!
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…
I’m so glad you liked it!
I don’t have a microwave. Can I use an oven to do this instead?Â
I have not tested it in the oven
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 🙂
I’m so glad you enjoyed!
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!
I’m so glad you enjoyed it!
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!!??
I’m so glad you enjoyed!
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!
I’m so glad you enjoyed the recipe!
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
I’m so happy you enjoyed!
I’m gonna try with unsweetened cocoa powder!
how big of a cake does this make?
it fills a 12 oz mug
Has anyone tried this with almond or macadamia nut butter?
I recently made an almond butter version https://kirbiecravings.com/3-ingredient-keto-almond-butter-mug-cake/
Hmm tempted to try with the chunky peanut butter I have ?
It works with chunky too
It’s awesome with chunky!
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.Â
I’m so glad you like it so much!
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.Â
So happy you like it!
Can I use honey as a sweetener?Â
I have not tested with honey.
I don’t have any sugar substitute and I’m not on keto I just love peanut butter and love the idea. Can I use just regular sugar if so how much?
I’m about to make the 2 ingredients brownies right now!
Hi Jess! You might like to try our Peanut Butter Mug Cake that has granulated sugar – it’s a three-ingredient recipe, too!
You didn’t say to butter the inside of the mug?????Â
You don’t need to. The cake will pull away from the sides when it is done.