These easy Keto lemon bars are a crowd-pleaser. They are super moist and just on the right side of zingy. Only 5 minutes prep and ready in just 40 minutes.
This recipe is a Sugar Free Londoner classic. It has been on the blog since 2019 and consistently gets 5-star reviews. "Delicious, light and fluffy," wrote a reader recently. She had just made it for the second time. "They come out perfect every time."
These keto lemon bars are definitely not traditional. In fact, when I first created this recipe, I was not aware that classic lemon bars have a shortbread crust and a lemon curd filling!
My recipe is essentially a keto lemon cake sliced into bars. Due to the addition of sour cream, it has a super moist crumb. I find there is a hint of baked cheesecake texture.
Classic or not, this is a truly delicious dessert experience. I am giving you plenty of topping options further down, including a sugar free lemon curd frosting.
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Ingredients
Here are the ingredients you'll need for easy sugar free lemon bars:
- Eggs - large. These must be at room temperature to help the cake rise better.
- Butter - Should be very soft. I warm mine in the microwave until it is almost melted.
- Sour Cream - room temperature. You could also use cream cheese.
- Lemon - We need both the juice and the zest. Make sure you buy unwaxed lemons. For me, 1 ½ lemons yielded ¼ cup lemon juice. For extra zing, you could increase the amount of lemon juice by up to 2 additional tablespoons.
- Almond flour - I've used ground almonds for this cake, which is equivalent to coarse/grainy almond flour. This helps with creating that super juicy sponge cake. Reduce the amount by ¼ cup (25g) for super fine almond flour.
- Baking powder - Check that it is fresh.
- Powdered sweetener - I used erythritol. However, this recipe will work just as well with Swerve, monk fruit sweetener blends, Bocha Sweet or allulose. Check that you are using a 1:1 sugar substitute.
See the recipe card for full information on ingredients and quantities.
Instructions
Let's make keto lemon bars! Here are step-by-step images. For more details, scroll down to the recipe card.
STEP 1
Beat the eggs until frothy. Then add the softened butter and the sour cream and blend in a food processor or with an electric mixer until combined.
STEP 2
Add the lemon juice, lemon zest and powdered sweetener and blend.
STEP 3
Last, add the remaining dry ingredients - almond flour and baking powder. Mix until smooth. Let the batter sit for a couple of minutes to thicken. It should be thick but pourable.
STEP 4
Line a small casserole dish or cake pan with parchment paper. I used a 9 x 6-inch dish, but it could even be slightly bigger - my cake bar slices were a generous 4 cm / 1.5 inch tall. Fill in the batter and smooth the top with a spatula.
STEP 5
Bake the cake on the middle oven shelf for 35-40 minutes or until a toothpick inserted comes out clean.
Expert Tip
#1 Use the lemon zest! It really lifts the flavor. It's my secret ingredient.
#2 Taste the batter and adjust the sweetener if required. I don't like my cakes too sweet. You may prefer a little more sweetness. There is no right or wrong here!
Toppings
I decided to keep it quick and simple and dusted powdered sweetener over the cake.
Here are more topping ideas:
Sugar Free Lemon Drizzle:
Mix 4 tablespoons lemon juice with 4 tablespoons powdered sweetener and drizzle over the cake.
Low Carb Lemon Glaze:
Stir together 4 tablespoons each of melted butter, cream, powdered sweetener and the juice of 1 lemon. Wait until the mixture starts to cool and thicken, then pour over the cake.
Simple Keto Lemon Cream Cheese Frosting:
Mix ½ cup cream cheese, 4 tablespoons of powdered sweetener, a squeeze of lemon juice and grated lemon zest. Spread over the lemon bars and grate extra lemon zest on top.
Pull-out-all-the-stops Keto Lemon Curd Frosting:
Make a batch of sugar free lemon curd and cool in the fridge. Whip 1 cup / 240ml of heavy cream until stiff and fold in the cold lemon curd. Spread over the cooled cake and grate lemon zest on top.
Substitutions
Coconut flour: I know some of you cannot have almond flour. You can try making this recipe using 1 cup of coconut flour in place of the almond flour plus an additional egg. A reader has tested this variation and reported that it works well.
Dairy-free: For dairy-free keto lemon bars, use coconut yoghurt or coconut cream in place of the sour cream. Also, use coconut oil or a dairy-free butter substitute.
Less fat: Use Greek yoghurt in place of sour cream.
Recipe FAQs
Yes! This recipe also works well in a loaf pan. The baking time will increase to around 45-50 minutes.
Yes, you can add â…“ cup of fresh blueberries into the cake batter. This way, it will taste similar to my keto blueberry bread.
Yes. Fill the batter into muffin liners and bake for 25 minutes. To make cupcakes, add the cream cheese or the lemon curd frosting described above.
Storage
Store keto lemon bars in an airtight container at room temperature for up to 2 days or in the fridge for up to 5 days.
All almond flour cakes freeze well. I pre-slice this cake into bars and freeze them for up to 3 months. This way, I can defrost one slice at a time overnight.
More Keto Lemon Desserts
- Easy Sugar Free Lemon Sorbet5 Hours 20 Minutes
- Keto Lemon Cookies40 Minutes
- Low Carb Lemon Cheesecake30 Minutes
- Keto Lemon Mug Cake3 Minutes
Tried this recipe? Give it a star rating below!
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Recipe
Keto Lemon Bars
from Sugar Free LondonerNote: The servings slider only changes the first amount in each line and not any subsequent amounts. Please make your own calculations where necessary.
Ingredients
- 4 eggs large, room temperature
- ½ cup / 120g sour cream room temperature
- ½ cup / 120g butter must be very soft
- ¼ cup / 4 tbsp lemon juice I used 1 ½ lemons
- zest of 1 lemon
- 2 cup / 200g almond flour Use 2 tablespoons less for super-fine almond flour
- 2 teaspoon baking powder
- â…“ cup / 40g powdered erythritol or more, to taste.
Instructions
- Preheat the oven to 175 Celsius / 350 Fahrenheit.
- Beat the eggs until frothy. Add the sour cream and softened butter and blend with a food processor or electric mixer until combined.
- Add lemon juice, the grated zest of 1 lemon and â…“ cup powdered erythritol or powdered sugar substitute of your choice. Blend.Â
- Lastly, add the almond flour and baking powder and mix until you have a smooth batter. Adjust sweetener to taste, adding more if required.Â
- Line a 9x6 inch pan with parchment paper and fill in the batter.Â
- Bake in the middles shelf of the oven for 35-40 minutes until the top is lightly browned and a skewer inserted comes out clean.
- Leave to cool completely before cutting or removing from the pan. Almond flour cakes are fragile when hot, but they firm up as they cool down.
Anna
I am planni On making this and would like to know if it can be frozen? Thanks
Katrin Nürnberger
Hi Anna, this cake freezes well. All almond flour baked goods do 🙂
Beth
This came out really well.Thank you! Ionly had super fine almond flour and it was still very good.
Katrin Nürnberger
Wonderful! Glad you enjoyed the cake.
JoyceK
Made these bars last night, waited for them to cool, and they began to fall apart when I cut them. Left them in the pan until this evening, and tried again, and there is a vast improvement in texture and flavor! As you have said, these products made with almond flour improve when held for a day before handling. The flavor was very nice, and not sweet at all. Next time, I think I will add 1 tsp of Lemon extract to bump up the lemon flavor; but that is purely personal! I liked the powdered erythritol on top too! This is a great recipe that I will put I my rotation! Thank you for this recipe and this site!! It's the best ever, esp. for baked goods!
Katrin Nürnberger
Yes, I think almond flour cakes just become a little juicier the next day!! You could also add more lemon zest next time you make the recipe, to up the lemon flavour. 🙂
Frank
Hi Is the nutrition calculated per piece of whole cake?
Katrin Nürnberger
Yes, I calculated per portion.
Angela
Yum. Best sugar free slice/cake I have found. My Type 1 diabetic 4 year old loves it too
Maxine
Thank you. I put sugar free jam with it. Just a touch which added to it. you are very clever. X
Katrin
Nice idea to add some sugar free jam to the cake!
Claire
Katrin ,
You are such an angel, sharing these yummy alternative recipes with us. I made this today in a loaf pan with collaborative coconut yoghurt (instead of sour cream ) and I used stevia as sweetener. It turned out brilliantly and the texture is so beautiful.
Thank you for a new favourite.
Claire xo
Katrin
So good to hear it works with coconut yoghurt!
Joan Shields
We just loved this lemon cake! I made it as directed the first time but with fine grind almond flour and part Splenda and eryithritol/ monk fruit blend. I iced it with cream cheese frosting to which I added lemon juice and Splenda for sweetener. The flavour and texture were just like a scratch cake I used to make before keto.
I made it again today and stirred a few frozen blueberries into the batter and backed a couple of minutes longer. I'm sure this will be even better.
Thank you for a great recipe!
Katrin
Blueberries in this cake would be delicious!!!
Maria
Other than the dust of powder sugar substitute, does this cake has any other sweetener??
Katrin
No, it's just the powdered erythritol. It's a 1:1 substitute for icing sugar. If you have granulated erythritol/xylitol, you can blitz it and make your own powdered version. I hope this helps 🙂
Klaudia
Could you add lime as well?
Katrin
Yes, absolutely!