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Sourdough Lemon Bars

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:

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

Sourdough Lemon Bars

These sourdough lemon bars have a light and flaky crust with a bright and zesty lemon curd filling.
Prep Time 15 minutes
Cook Time 42 minutes
Total Time 57 minutes
Course Dessert
Cuisine American
Servings 24 cookies
Calories 94 kcal

Ingredients
 
 

For the Crust

  • 1 cup unsalted butter
  • cup powdered sugar (confectioner's sugar)
  • cup sourdough starter active starter or unfed discard from the fridge
  • 1 teaspoon vanilla extract
  • 1 teaspoon salt
  • cup all purpose flour

For the Lemon Filling

  • 6 large eggs
  • 2 cups granulated sugar
  • ½ cup sourdough starter
  • 1 tablespoon lemon zest about 2-3 lemons
  • 1 cup lemon juice 4-8 lemons depending on size
  • ¼ teaspoon salt

Instructions
 

  • Preheat oven to 350℉.
  • Line a 9×13 inch baking dish with parchment paper. (The edges of the parchment paper should come up the sides of the pan on two opposite sides. This will let you lift the lemon bars easily from the pan after baking). Set aside.
  • In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and powdered sugar on medium speed.
  • Add the sourdough starter, salt and vanilla and mix until combined.
  • Set the stand mixer to low speed and slowly add the flour. Mix until just fully combined.
  • Press the dough evenly into the bottom of the prepared baking pan to form the bottom layer of crust.
  • Bake the crust for 20-23 minutes or until starting to turn golden brown.

Prepare the Lemon Filling

  • In a large bowl, whisk together the filling ingredients (eggs, sugar, sourdough starter, lemon zest, lemon juice, and salt) until smooth.
  • Pour the mixture over the crust while still warm from the oven.
  • Reduce heat in oven to 325℉.
  • Bake the lemon bars for 20-23 minutes or until the mixture is just fully set. It should wobble but not appear wet when done.
  • Allow to cool in pan completely at room temperature (about 45 minutes).
  • Use parchment paper to gently lift the bars from the pan. Dust with extra powdered sugar through a mesh sieve.
  • Cut the bars into approximate 2 inch squares and serve.

Nutrition

Calories: 94kcalCarbohydrates: 11gProtein: 1gFat: 5gSaturated Fat: 3gPolyunsaturated Fat: 0.2gMonounsaturated Fat: 1gTrans Fat: 0.2gCholesterol: 14mgSodium: 66mgPotassium: 10mgFiber: 0.2gSugar: 5gVitamin A: 158IUCalcium: 3mgIron: 0.4mg
Keyword Bars, Easy, mother’s day, Sourdough, Sourdough Discard
Tried this recipe?Let us know how it was!

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7 Comments

  1. Made them!
    Delicious! I did have to switch up because I didn’t have enough butter so about 80g of my fat was coconut oil. It was still very very delicious! Wow!

    1. Thank you for the feedback! I’m glad to hear they worked out with the coconut oil as well!

  2. Does the starter need to be active for both the filling and the crust or can I use discard for both?

    1. Hi Brandi!

      I haven’t tried it but I think the texture of the filling might get a bit weird in freezer.

  3. I wanted to share an update from my last comment. These actually came out amazing in the end!! Yay!! Idk why the filling was so runny and ran out over the sides of the crust, but it ended up working. The filling all settled at the bottom of the pan. Once they were totally cooled, I lifted the parchment paper to pull the bars out of the pan. I flipped them and wouldn’t you know the filling had totally thickened on the bottom. They looked perfect and tasted sooo good!! The lemon flavor was the perfect balance is sweet and tart. Now that I figured it out I’ll be making again! So sorry for my confusion. 🤪

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