Simple Sustainable Sovereign

The Perfect Summer Treat

Sourdough lemon bars are a tart, sweet, refreshing dessert that is absolutely perfect for a summer treat. I’ve been making lemon bars since my sister and I first picked a lemon bar recipe for our homeschool home economics class when I was around 11. Every time I make them I am appreciative of their light and bright taste. They remind me of sunshine shining through the windows as spring comes to a close and summer arrives in full swing. This recipe, with its sourdough shortbread crust, lemon curd filling, and dusting of powdered sugar is sure to delight. It’s the perfect pick for your next barbecue, or as a cure to your winter blues.

Why Make Lemon Squares with Sourdough?

This recipe, while largely the same as the one I followed as a kid, has gotten a little upgrade with the addition of fermentation. Using sourdough starter in the crust and curd allows for easier digestion of the grains in this dessert, as the fermentation process of sourdough breaks down the phytic acid present on wheat, making it is easier for your body to process.

I’ve been using sourdough starter in every recipe I can since I first made my starter in 2019. I find that it elevates any baked good by adding an additional layer of flavor that just isn’t present in unfermented pastries. Try it and taste the difference!

A Note on Fermentation

This recipe is a great way to use up sourdough discard, as you can use fed or unfed started in this dessert.

Because this is a discard recipe, the fermentation time is flexible and can be adapted to fit your needs. You can even skip the fermentation time for the shortbread crust and go straight to baking if you are trying to save time. This will not give you the digestive benefits of sourdough, but you will have the added sourdough flavor in the final product. I generally ferment these on the counter for a couple of hours, but if you would like to really improve the digestibility of the grains, I would recommend long-fermenting the shortbread crust in the refrigerator for 12-24 hours, up to 3 days.

How to Make Sourdough Lemon Squares

Ingredients & Tools

For Sourdough Shortbread Crust:

• 16 Tbsp. Butter (1 cup) – Softened.
• 1/2 cup Sugar
• 1.5 tsp Vanilla Extract – I prefer homemade vanilla extract.
• 1/4 tsp Salt
• 1/2 cup Sourdough Starter – Active starter or discard can be used for this recipe.
• 2.5 cups Flour
• Stand Mixer with Paddle Attachment
• 9×13 inch Glass Baking Dish- Lined with Parchment Paper.

For Lemon Curd Filling:

• 7 Large Eggs
• 2 cups Sugar¹
• 2 Tbsp Lemon Zest – From 2 large, 3 medium, or 4-5 small lemons.
• 1 cup Lemon Juice² – Use fresh squeezed for best taste.
• 1/2 cup Sourdough Starter
• Powdered Sugar – For dusting on after baking.
• Large Bowl
• Whisk

Directions

1. Make the Crust: Begin by creaming together butter and sugar in the stand mixer using the paddle attachment. Stop to scrape down the sides as needed. Once light and fluffy, mix in vanilla extract, salt, and sourdough starter. Slowly add in the flour, one half cup at a time, until well combined. Evenly flatten the dough into the parchment lined baking dish.
2. Ferment the Crust: Leave the crust, tightly covered, at room temperature for 30 minutes to 2 hours, or place in the refrigerator to long ferment for 12-24 hours. You can also skip the fermentation and bake immediately.
3. Bake the Crust: Once finished fermenting, bake the crust in a preheated oven at 350^oF for 18-20 minutes until edges are just beginning to turn golden brown. Remove from the oven and allow to cool slightly on a wire rack while you make the filling.
4. Make the Filling: Whisk together eggs, sugar, lemon zest and lemon juice until well combined. Add the sourdough starter and whisk until fully incorporated. Pour over the slightly cooled crust.
5. Bake and Cool: Bake the tart for 30-35 minutes at 350^oF until it no longer jiggles in the middle. Remove promptly to avoid overbaking. Allow to cool at room temperature for an hour or so before placing in the fridge. Cool completely before slicing to serve.
6. Serve: Remove lemon bars from the pan using the parchment paper. Sprinkle with a light layer of powdered sugar and slice into 15-20 bars. Serve and enjoy! Store refrigerated.

Notes:

1. I find that 2 cups of sugar in the curd is the perfect balance between tart and sweet, especially with the added powdered sugar on top, but if you prefer a less tart dessert, up the sugar to 2.5-3 cups. ↩︎
2. Don’t use more than one cup of lemon juice or the curd will be too wet and will not set. ↩︎

Did you try this recipe? Let me know what you think in the comments below.

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