Lemon is one of my favorite flavors for the warmer months (also see my lemon blueberry sourdough scones and my lemon shortbread cookies with lemon glaze). Whether it’s a picnic, a tea party, a baby shower, or a holiday like Easter or Mother’s Day, this bright and cheery flavor is sure to fit right in your menu. My sourdough lemon bars are a classic treat that I am so excited to share with you. This recipe is truly so delicious and easy to make. There is sourdough starter in both the crust and the filling but your friends and family will have no idea.

Why You Will Love these Sourdough Lemon Bars

This lemon bar recipe is perfect for lemon lovers and can be made start to finish in a couple of hours. They use a generous amount of sourdough discard as it is present in both the crust and the filling. I love that the delicious buttery crust strikes the perfect balance with the lemon layer that sits on top. They are the perfect way to satisfy your sweet tooth without overwhelming sweetness or richness. I truly think these are the best lemon bars and I hope you do too!

Sourdough lemon bars on a baking sheet lined with parchment paper, The bars have been dusted with powdered sugar and cut into individual squares.

I modified my classic shortbread cookie recipe (which is one of my most popular recipes) to use as the base of these bars. The only difference I made to my original recipe is substituting confectioner’s sugar for the regular sugar. This substitution creates a delightfully light texture while maintaining a delicious buttery shortbread crust.

How to Use Sourdough Starter in Lemon Bars

The obvious place to use the sourdough starter is in the crust, but I also added it in the filling. Some recipes for classic lemon bars call for a small amount of flour and other liquids in the filling, which can easily be replaced with sourdough starter.

Ingredients and Substitutions

For the Shortbread Base

sourdough lemon bar shortbread crust ingredients in individual measuring cups and bowls.

Butter: We use unsalted butter but you can also use salted butter if desired. Reducing the salt in the recipe by half can help them not come out too salty.
Sugar: We use powdered sugar (also known as confectioners sugar) for this recipe. This creates a lighter and fluffier texture. You can also substitute regular granulated sugar and it will still taste delicious. The texture will just be slightly coarser.
Sourdough starter: You can use active starter or discard from the fridge. I recommend weighing the starter if you are using active sourdough starter as it will be less dense due to the air bubbles.
Vanilla
Salt
Flour: You can use all purpose flour or bread flour for this recipe.

For the Lemon Filling

sourdough lemon bar filling ingredients in individual measuring cups and bowls.

Eggs: We need whole eggs for this recipe.
Sugar: For the filling we use plain white sugar. I have not tested this recipe with any alternatives so I cannot recommend any substitutions.
Sourdough starter
Lemon zest
Lemon Juice: You need LOTS of fresh lemons for this recipe in order to achieve that perfect lemon flavor. Depending on the size and juiciness of the lemons you will need anywhere from 4-8. I highly recommend fresh lemon juice in this recipe as most bottle lemon juices contain extra ingredients and are made from concentrate. This can affect the flavor of the bars. If you want to mix it up a bit, you can use meyer lemons in this recipe. Meyer lemon bars will be sweeter and less acidic.
Salt

How to Make

Make the Crust

Step 1: Cream butter, sugar and lemon zest.

Step 2: Add starter, salt and vanilla.

Step 3: Add flour.

sourdough lemon bar shortbread crust dough in bowl of stand mixer fitted with paddle attachment.

Step 4: Line a 9×13 inch baking pan with parchment paper for easy removal when the bars are finished baking.

Step 5: Press the dough into the base of the baking pan.

sourdough lemon bar crust dough pressed into a 9x13 inch pan.

Step 6: Bake for 20-22 minutes or until the crust begins to turn golden brown.

Make the Lemon Curd Filling

Step 1: Whisk together all filling ingredients in a large bowl.

sourdough lemon bar filling ingredients in large bowl with whisk.

Step 2: When the crust is finished baking, whisk the lemon curd mixture again and pour over the crust.

Step 3: Bake for 20 minutes. Bake times may vary slightly so check for signs of doneness (not wet appearing and somewhat firm when gently touched).

baked sourdough lemon bars before dusting with powdered sugar.

Step 4: Allow to cool completely in the pan. The bars will cool faster if you place the pan on a wire rack.

Step 5: Remove from pan, sprinkle with powdered sugar, and cut into squares.

How to Make Ahead

I don’t recommend making these bars more than 2 days ahead of time. Store the bars in the fridge and top with powdered sugar when ready to serve.

How to Store

Because these bars have an egg custard base, they need to be stored in the refrigerator in an airtight container or on a plate wrapped in plastic wrap. I recommend using within 2-3 days.

I hope you enjoyed this sourdough take on traditional lemon bars. If you did, will you please leave a star rating? It is hugely helpful for my site to get your feedback.

If you love sourdough, check out these other delicious sourdough recipes: