Keto Lemon Bar Recipe

Enjoy a delicious and lightly tart keto lemon bar using a flaky gluten free shortbread base, paired with a tangy lemon filling you know and love.

Whether it’s a hot summer day or you just simply love lemons, there is something so classic about a delicious lemon bar. These bars are gluten free (the shortbread crust is made from almond flour) and I have perfected the simplest keto friendly lemon filling too.

This is a great alternative if you follow a ketogenic diet or possibly struggle with insulin resistance (or are just looking to cut down on carbs).

Each Bar is only two net carbs as well! The perfect after dinner dessert. The best part? You would never know these weren’t made with traditional ingredients like flour or granulated white sugar.

Baking can often feel intimidating (especially when using gluten free or keto ingredients); let me help you master this delicious baked good with confidence!

Below you will find helpful baking instructions and techniques to make an incredible keto friendly lemon bar. Let’s dive in!

Supplies Needed

• Food Processor
• Measuring Cups/Spoons
• 9×9 Baking Pan
• Parchment Paper
• Spatula 

Is Lemon Keto?

I know you might be wondering if lemon can properly fit into a keto diet. I also wondered the same thing! The good news is that lemon is in fact keto. Lemons are low in sugar with about 4 net carbs per lemon, and they contain Vitamin C and Pectin which are both associated with health benefits!

Keto Lemon Bar Ingredients:

For the Shortbread base:

• Almond Flour

• Low Carb Sweetener- Something like Allulose or Lakanto

• Baking Powder

• Xanthan Gum

• Salted Butter

• Vanilla or Almond Extract

• Egg

For the Lemon Filling:

• Egg Yolks

• Fresh Lemon Juice

• Low Carb Sweetener- Something like Allulose or Lakanto

• Xanthan Gum

• Powdered Low Carb Sweetener- Optional

Can I Omit Xanthan Gum?

One of the most common questions I get about keto baking is in regards to using xanthan gum. Yes, it is necessary.

Xanthan gum acts as a binding agent in place of the gluten that’s been removed from this recipe (i.e swapping almond flour for a classic white flour). Because almond flour is a lot denser, it often can get crumbly when it’s been baked.

Xanthan gum works to help bind and keep the almond flour together in the way regular flour would bake up in my opinion.

This is helpful for keto-friendly desserts. Your bars will be intact, easy to eat, and won’t fall apart!

If you don’t have xanthan gum some possible substitutions (though I haven’t tried) would be cornstarch or arrowroot root starch. Just calculate that into your total carbs at the end. 

What if I don’t have a Food Processor?

No food processor? Though I have to say the food processor is the best way to go, your other option would be to freeze your butter and grate it into the dry ingredients.

Use a hand mixer then to combine everything thoroughly. I pre-bake the dough in a parchment paper-covered pan (it makes clean-up so easy), poke holes with a fork in it so it doesn’t bubble up, and let it cool just slightly before adding the filling.

Keto Lemon Bar Shortbread Base

This base is my go-to for shortbread. I used it as the base for my Keto and Gluten Free Samoa Girl Scout Cookie recipe and even worked as a gluten-free and keto-friendly pie crust too.

It will be a staple for you when making many keto-friendly desserts. What I love the most about this recipe is that it is only a handful of ingredients, a few pulses in the food processor, and it comes together in what feels like 5 minutes.

1. Preheat the oven to 350 F. (Please note you will lower the temperature when you bake with the filling) and line a 9×9 inch pan with parchment paper (or grease well but parchment is the best option).

2. In a food processor, combine the almond flour, sweetener, baking powder, and xanthan gum and pulse a few times to combine. Add the very cold butter and pulse again until the mixture is combined well. Finish with the egg and the vanilla and blend until it’s one solid mixture that resembles cookie dough. If you do not have a food processor, see the notes in the post above for how to best make the shortbread base.

3. Press the base evenly into the 9×9 inch pan use a fork to poke a few holes across the top (prevents air bubbles) and bake at 350 F for about 15 minutes. The edges should look lightly golden brown. Allow it to sit for a bit before adding the filling (I wait to make the filling once this comes out first).

Keto Lemon Bar Filling

This filling is incredible. It reminds me so much of my grandma’s lemon meringue pie and I find it so rich and flavorful and a good balance between tart and sweet.

I tested this recipe two times and found a few tips I’d like to recommend for the filling, found in the steps below. Keep in mind that this filling has only been tested with Allulose and Lakanto sweeteners, so if you try a different one it might come out slightly different!

1. To make the filling, beat the 6 eggs very well in a bowl to start. In a separate bowl, whisk the sweetener and xanthan gum together well. DO NOT SKIP THIS STEP or you may end up with chunks of undissolved xanthan gum in your filling.

2. Combine the dry ingredients with the eggs and beat until combined well. Finally, whisk in your lemon juice and blend everything by hand until it looks like one solid, cohesive mixture.
3. Slowly pour the mixture over the shortbread base and pop back in the oven. Be sure to remember to bump the temperature down to 325 F or they will overcook!

4. Bake for about 22-25 minutes. The center should be set but slightly jiggly. You might notice that it looks a little bit wet in the middle. That is okay, as it will sit in the fridge. Remove from the oven and let it rest a bit at room temperature before putting it in the fridge. I find they set best after at least a few hours in the fridge. I know… patience is hard.

5. Top with some low-carb powdered sugar or leave and eat as is. Gluten-free keto lemon bars will last for a good week in the fridge (if you don’t eat them all by then). I freeze them as well and defrost individual ones as desired for a late-night treat too!

Baking and Storage Tips

• Let the bars cool for 3-4 hours before slicing. You want to make sure they are nice and set before you slice into them!
• Wipe the knife clean between each slice for clean-cut bars. Nothing is more satisfying than those clean edges!
• You can garnish your gluten free keto lemon bars with keto friendly powdered sugar or a keto friendly whipped cream.
• Store your lemon bars in an airtight container in the fridge.
• These bars are best when eaten within 3-4 days, but it would be surprising if you had any left by then anyway!
• If freezing, freeze them each individually and then take them out as you want them. It is best to defrost these in the fridge before serving.

If you’re a lemon lover like me, check out my Keto Ricotta Lemon Poppy Seed Scones recipe too! It’s easy and delicious as well. Or if you just have a sweet tooth and want some good keto friendly dessert options, try my Keto and Gluten Free Thin Mints, my Low Carb Sweet Potato Pie Bars, or my Keto Shortbread Sugar Cookies!