Kirbie's Cravings

Keto Lemon Mug Cake

This low carb and keto-friendly mug cake is bursting with lemon flavor. It’s a single serving cake that cooks in the microwave in less than two minutes.

overhead photo of a keto lemon mug cake

Lately, I have really been loving creating low carb mug cakes. When I wrote my mug cake cookbook* a few years ago, I felt like I exhausted every flavor combination possible for a regular mug cake. But low carb mug cakes are a whole different territory and it’s definitely reignited my desire to create new mug cakes.

So far I’ve made low carb snickerdoodle mug cake, blueberry mug cake, peanut butter mug cake, and brownie mug cake, just to name a few. This lemon mug cake is sweet and bright and reminds me of lemonade and summer.
photo of a lemon mug cake

Lemon Flavored Mug Cake

This cake gets its lemon flavor from both lemon juice and lemon zest. The lemon juice soaks into the batter and makes the batter ultra-moist. The lemon zest really enhances the lemon flavor throughout the cake.

I highly recommend that you take the extra minute or so it takes to grate some lemon zest for this recipe. When I first started baking many years ago, I used to always leave zest out of recipes because I didn’t think it was necessary. But especially with citrus recipes, it makes a huge difference. It really rounds out the lemon flavor so you don’t feel like you’re just eating a lemon juice cake.

Low Carb Flour Substitutes

This cake is made with a combination of superfine almond flour and coconut flour. The recipe only needs a tiny bit of coconut flour, but it is essential to this recipe coming out correctly. I prefer almond flour cakes because I find that they come out more light and moist. But a little bit of coconut flour is needed to soak up the lemon juice. Coconut flour is highly absorbent so you need to make sure you don’t add too much or it will make the cake dry.

Mug Cake Cooking Tips

  • This cake does not rise that high. I made it in an 8 oz mug.
  • Try to stick to a standard shaped mug. Mugs that are unusually tall or odd-shaped can result in the batter not cooking evenly.
  • The lemon juice tends to sink a little towards the lower half of the cake. To make sure there is enough lemon flavor throughout, I added a little bit of lemon zest to the top of the cake before cooking it.
  • The cake is best consumed shortly after it is cooked.
  • The cake can be topped with toppings of your choice. I kept it simple with some powdered Swerve.

For a large cake be sure to check out my keto lemon cake, too.

photo of a keto lemon mug cake

Keto Lemon Mug Cake

Servings: 1
Prep Time: 5 minutes
Cook Time: 2 minutes
Total Time: 7 minutes
Course: Dessert
Cuisine: American
A light cake bursting with lemon flavor. This cake cooks in the microwave in less than 2 minutes!
4.94 from 15 votes


  • 1 tbsp unsalted butter melted
  • 1 large egg
  • 3 tbsp superfine almond flour
  • ¼ tsp coconut flour
  • ½ tsp baking powder
  • 1 ½ tbsp erythritol sweetener granular
  • ¼ tsp vanilla
  • 1 tbsp lemon juice
  • ¼ tsp lemon zest plus additional for topping


  • In a microwave-safe mug that can hold at least 8 oz of liquid, add all mug cake ingredients except lemon zest. Mix with a small whisk until batter is smooth.
  • Stir in 1/4 tsp lemon zest. Add a little more zest over surface of the cake. This should only be about a pinch worth spread out across the surface.
  • Cook the cake in the microwave for about 1 minute and 40 seconds. Let cake cool slightly before dusting with powdered sugar substitute (like Swerve) or other topping of your choice. Cake is best consumed shortly after it is cooked.


  • I use an 1100 watt microwave. You may need to adjust time and/or power if you are using a different wattage.
  • I used So Nourished Erythritol Sweetener Granular* but you can use any granular sugar substitute of your choice. I prefer using erythritol because it doesn't have that cooling sensation.
  • The coconut flour is essential to this recipe. The cake will not be able to asborb all the lemon juice and will not rise properly without it. At the same time, you need to make sure you only use 1/4 tsp of coconut flour. Coconut flour is highly absorbent so if you use even a little bit extra, your cake will come out dry.
  • The cake does not rise that high so using an 8 oz mug should be sufficient.
  • Adding just a little extra lemon zest to the surface of the cake will help ensure lemon flavor throughout the cake because the juice does tend to sink a little towards the bottom of the cake.
  • *Some of the 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 carbs from erythritol


Serving: 1cake, Calories: 298kcal, Carbohydrates: 8g, Protein: 10g, Fat: 26g, Saturated Fat: 10g, Sodium: 69mg, Fiber: 3g, Sugar: 2g, NET CARBS: 5

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

48 comments on “Keto Lemon Mug Cake”

  1. I was craving cake so badly tonight – this recipe completely satisfied the craving while still keeping me inside of my macro goals for the day. I used 1/4 tsp. of coconut sugar instead of erythritol – and I think next time, I’ll sprinkle just a bit of unsweetened coconut on top along with the lemon zest. This is a winner and a lifesaver – thank you so much!

  2. This was amazing. I sprinkled Lily’s chocolate on top and it was so good. Thank you for sharing this.

  3. I also added a 1/4 tsp of lemon extract, and 1 tsp of water just because I find the water really helps to make things more moist. Absolutely delish, and takes seconds to make! You can never have too much lemon flavor!

  4. Love this recipe. I like add a few blueberries to it.

  5. I don’t usually leave comments on blogs but this was amazing, thank you so much for creating this recipe. I followed another post advise about 4tbs of almond flour as that’s all I had. Doesn’t taste like a keto cake. Very light and moist. I added extra zest as I love lemon. Going to explore more if your site now ?

  6. I just tried this and loved it. I used lemon extract instead of vanilla. I will be making this again! Thank you for the recipe!

  7. Okay I am making this every day! Easy and quick and delicious. The consistency was good, no weird taste. I put a little cream cheese mixed with lemon juice on the top. A lifesaver for my nightly treat!

  8. OMG I just made the mug cake and am in HEAVEN! Thank you soooooooooooooooo much! x

  9. I just finished making your Lemon Mug Cake for the first time.  I used melted butter, monk fruit sweetener and forgot to add the coconut flour.  Oh my goodness.  This was so delicious.  I’ll be treating myself to this amazing dessert again. Thanks for a terrific …and forgiving recipe.

    • That’s great to hear! Thanks for letting us know.

      • Just made this mug cake after suffering a bout of bad bacteria from antibiotics. Watching my family enjoy lemon cake while I sit back without as I have to eliminate sugar. So glad I found this recipe! I used bob mills almond flour blend which worked a treat! Also drizzled lactose free yogurt sweetened with monk fruit and lemon juice and rind. Delicious ? 

      • Glad you enjoyed it!

  10. Delicious!! 

  11. Delicious! We loved this little easy cake for one.

  12. Delish….glad we tried it

  13. Following a Keto diet and missing cake. This was the first mug cake I’ve ever made and what a treat it was. 
    Scanned all the ingredients to Nutrachevk app and was a bit alarmed by the volume of carbs and calories but I’ll go easy the rest of the day it was totally worth it. 

  14. If you love lemon you will love this muffin.

  15. The best mug cake I’ve made!! I absolutely love how moist and full of flavor this is. And, it doesn’t feel grainy like a lot of cakes made with almond flour. How can I increase this recipe and bake in the oven to make a full size cake or cupcakes? What temp setting should I use?

  16. This was so good! It was so smooth and moist. Didn’t taste like a lemony scrambled egg, like most mug cakes made with a whole egg. I used Allulose sweetener. I think lemon desserts are best served room temp or even chilled, but I was too greedy to wait. Printed out and added to my make again Pinterest board. HIgh praise! Few new recipes make to either place. Thanks again!

  17. Delicious ~ very satisfying. I love lemon and this made me happy ?

  18. Can I find erythritol sweetener in a regular grocery store

    • some grocery stores like Whole Foods carry Swerve. It’s also sold at Costco. I find it cheaper to buy on Amazon or at Costco

  19. Delicious!!!! I only had almond flour so I used 4 tbs and it was perfect!!!! I love lemon so when it came out, I poured a bit more lemon juice on top. Next time (as in tomorrow night) I’ll make a lemon icing. Soooo good! 

    I’m trying to give this a 5 star rating, but for some reason it keeps changing to 4. 

  20. Just made this and topped it with sugar-free lemon curd. Super delicious!

  21. Absolutely delicious! Great recipe, I’ll be following you for more ?

  22. What a great treat! I’m sorry I didn’t post a photo, but we ate them before we could snap a pic! So good!

  23. Love this lemon cake!  Super lemon taste, perfect fluffy texture.  Made exactly as written.  I have eaten MANY mug cakes and this is one of my all time favorites I keep going back to.  Make sure to dust the top with powdered sweetener sugar.