Sourdough lemon bars put a bright, tangy spin on a timeless dessert. For the creamiest filling and a tender shortbread crust, bring your eggs and butter to room temperature before you begin. These bars use sourdough discard in the crust for a subtle, complex flavor that sets them apart from the ordinary lemon bar.
Sourdough Lemon Bars
Katie Shaw
Ingredients
For the Crust
- 1 cup all-purpose flour
- ⅓ cup sugar
- ½ cup unsalted butter, cold and cubed
- ½ cup sourdough discard
Lemon Filling
- ½ teaspoon salt
- 1½ cups sugar
- 2 tablespoons cornstarch
- ½ teaspoon salt
- ¼ cup water
- 5 egg yolks
- 2 whole eggs
- ⅔ cup lemon juice (freshly squeezed for best flavor)
- 1 lemon zest
Assembly
- Powdered sugar for dusting
Instructions
- Preheat the oven to 350°F (175°C). Line a 9×9 or 8×8 inch baking pan with parchment paper or spray it lightly with cooking spray.
- Prepare the crust. In a medium bowl, mix flour, sugar, and a teaspoon of salt. Cut in the cold, cubed butter using a fork, pastry cutter, or your fingers until the mixture resembles coarse crumbs. Add the sourdough discard and mix gently until the dough begins to come together; it will be similar to pie dough.
- Press and bake the crust. Press the dough evenly into the bottom of the prepared pan. Bake 15–20 minutes, until lightly golden. Remove from oven and let cool slightly.
- Make the lemon base. In a medium saucepan, whisk together sugar, cornstarch, and ¼ teaspoon salt. Stir in the water, lemon juice, and lemon zest. Cook over medium-high heat, stirring frequently, until the mixture comes to a boil. Reduce heat and simmer for 1 minute until it thickens.
- Temper the eggs. In a small bowl, whisk the egg yolks and whole eggs. Slowly whisk about ½ cup of the hot lemon mixture into the eggs to temper them and prevent curdling.
- Finish the filling. Pour the tempered eggs back into the saucepan and continue cooking, stirring constantly, until the mixture returns to a gentle boil and thickens, about 2 minutes. Remove from heat and stir in 2 tablespoons of butter until smooth and fully incorporated.
- Assemble and bake. Pour the lemon filling over the baked crust, smoothing the top with a spatula if necessary. Bake 20–25 minutes more, until the filling is set. Allow to cool to room temperature, then chill for at least 2 hours to fully set.
- Finish and serve. Dust with powdered sugar, cut into bars, and serve chilled.
Notes
Bring key ingredients to room temperature before mixing—this helps the filling become smooth and prevents the crust from overworking. For a brighter lemon punch, increase the amount of lemon zest. Chill the bars thoroughly before cutting for cleaner slices.
Nutrition (per bar)
Calories: 138 kcal | Carbohydrates: 21 g | Protein: 2 g | Fat: 5 g | Saturated Fat: 3 g | Sugar: 15 g
I’ve made these lemon bars for family gatherings, potlucks, and simple at-home treats. They disappear quickly and are always a crowd-pleaser—even picky eaters dig in. Letting people dust their own pieces with powdered sugar is a fun little finishing touch that kids especially enjoy.
Key Ingredients and Tools
- Sourdough discard. Adds a subtle tang and depth to the crust. Use fresher discard for a milder flavor or older discard for more tang.
- Fresh lemons. Freshly squeezed lemon juice and zest provide bright, vibrant flavor—bottled juice won’t taste the same.
- Cornstarch. Essential for thickening the lemon filling so it sets properly.
- 9×9 or 8×8 baking pan. The pan size determines the final thickness; use what the recipe calls for to achieve the best texture.
- Parchment paper. Makes removing the bars and cleaning up simple.
- Medium saucepan and whisk. A heavy-bottomed saucepan ensures even heating; a whisk keeps the filling smooth and lump-free.
- Zester and juicer. For efficient extraction of zest and juice and maximum lemon flavor.
Troubleshooting and Help
Yes, in a pinch, but fresh lemon juice will deliver a brighter, fresher flavor that bottled juice cannot match. Fresh juice and zest are worth the extra effort when possible.
A similar-sized pan such as 7×11 inches will work. Monitor the baking time, which may be shorter or longer depending on the pan dimensions. Aim for a lightly golden crust and a set filling.
Yes. Substitute the all-purpose flour in the crust with a 1:1 gluten-free flour blend designed for baking. Results vary by blend, so choose one suited for shortbread-style crusts.
Store in an airtight container in the refrigerator for up to 5 days. They also freeze well: individually wrap bars, place in a freezer-safe bag, and freeze up to 3 months. Thaw overnight in the fridge before serving.
Lemon Bar Tips
- Sourdough discard age: Older discard gives a stronger tang; fresher discard gives a subtler profile.
- Lemon variety: Meyer lemons are sweeter and less acidic than standard lemons and can change the flavor profile if you prefer a milder, sweeter filling.
- Chilling: Chill the bars thoroughly before slicing for clean, neat pieces.
Storing Leftovers
Refrigerating:
- Place cooled bars in an airtight container. If stacking, separate layers with parchment paper.
- Refrigerate up to 5 days.
Freezing:
- Wrap each bar individually in plastic wrap, then place in a freezer-safe bag or container.
- Freeze up to 3 months. Thaw overnight in the refrigerator before serving.
Next time you want a refreshing, tart dessert with a little extra character, try these sourdough lemon bars. They combine classic lemon flavor with the subtle complexity of sourdough discard for a memorable treat.