I’ve loved this sourdough lemon sheet cake recipe for years, and it never disappoints. The moist cake, the amazing lemony buttercream, and that subtle sourdough tang. A sourdough discard recipe that your family will ask for seconds every time.

Sourdough Lemon Sheet Cake with Lemon Buttercream

A bright, sunny lemon sheet cake that transforms your sourdough discard into a bakery-worthy dessert the whole family will love.

Prep Time 15

Cook Time 35

Total Time 50

Serving Size slices

Equipment

stand mixer or hand mixer
Large mixing bowl
saucepan
13×9 inch baking pan

Ingredients

Cake

2 cups all-purpose flour
1 teaspoon salt
1½ teaspoons baking powder
½ teaspoon baking soda
4 large eggs
1¾ cups sugar
¾ cup sourdough discard 100% hydration, at room temp
¾ cup milk
¼ cup butter room temperature (cut into tablespoon pieces)
⅓ cup vegetable oil
2 tablespoons lemon zest
1½ tablespoons lemon juice
2-3 drops yellow food coloring optional

Lemon Buttercream

1 cup unsalted butter softened (2 sticks)
4 cups powdered sugar
1½ tablespoons lemon zest
2 tablespoons fresh lemon juice
2 tablespoons heavy cream
Pinch salt
Additional lemon slices or zest for garnish

Want To Save This For Later?

I’m email you a link so you can find it when you need it.

You'll join my email list which you will love. And if you don't, unsubscribe in one click. ❤️

Instructions

Prep. Preheat your oven to 325°F with a baking rack in the center. Grease your 13×9-inch pan with non-stick spray.
Mix Dry Ingredients. In a medium bowl, whisk together the flour, salt, baking powder, and baking soda.
Beat Eggs & Sugar. In your stand mixer bowl or another large mixing bowl, beat the eggs and sugar at medium-high speed for 2–3 minutes until the mixture is very light and fluffy.
Add Sourdough Starter. Gently mix in the sourdough discard until just combined.
Combine Dry & Wet. Add the dry ingredients to the egg mixture and beat until just incorporated—scraping down the sides if needed.
Heat the Milk Mixture. In a small saucepan, heat the milk with the vegetable oil and butter until it's just beginning to simmer. Remove from the heat.
Fold In Milk & Lemon. Gently fold the warm milk mixture into the batter. Then, stir in the lemon juice, lemon zest, and food coloring if using.
Bake. Pour the batter into your prepared pan and bake for 30-35 minutes. (The cake might look a bit spongy—that's normal.) Test with a toothpick; it should come out clean.
Cool. Allow the cake to cool completely in the pan before frosting.
Make the Lemon Buttercream. Beat the butter, powdered sugar, lemon zest, lemon juice, salt, and 1 tablespoon heavy cream in your stand mixer. Add a bit more cream if needed until you reach your desired frosting consistency.
Assemble. Spread the buttercream evenly over the cake. Top with thin lemon slices or lemon zest curls. Serve straight from the pan, and store any leftovers in an airtight container in the fridge.

Video

Notes

Sourdough Flavor: The discard adds a slight tang that complements the lemon. If your starter is very tangy, you might adjust the lemon juice to taste.
Baking Time: Because a 13×9 pan makes a slightly thicker cake than a jelly roll pan, your bake time will likely be shorter than the original. Start checking at 25 minutes.
Storage: The cake stays delicious for up to a week in the fridge. It also freezes well if wrapped tightly.
Make Ahead: You can bake the cake a day ahead and frost it just before serving.

The method here is slightly different from traditional cake-making. Adding warm milk and butter creates a texture between a sheet cake and a sponge cake – light but still sturdy enough for a layer of frosting.

slice of lemon cake with lemon wedge on top on blue and white plate.

Heating the milk with butter and oil before adding it to the batter creates the ideal environment for the sourdough and leavening agents to work together, giving the cake its distinctive texture.

Kitchen Wisdom

Combining sourdough with citrus is an old baker’s trick that balances flavors naturally. The slight sourness of the discard means you can use less lemon juice while still getting a bright flavor, making your lemons stretch further.

Tips for Success

Room temperature ingredients: Bring your eggs and discard to room temperature. Cold ingredients will shock the warm milk mixture and create a dense texture.

Don’t overmix: Once you add the flour, mix just until combined to avoid developing gluten that makes your cake tough.

Look for visual cues: The cake is done when it’s just starting to pull away from the sides and a toothpick comes out clean. The top might still look slightly moist – that’s normal.

Cool completely before frosting: If you frost while warm, you’ll end up with melted buttercream sliding off the cake.

For smooth frosting: Make sure your butter is truly softened before making the buttercream to avoid lumps.

Ingredients and Equipment

Sourdough discard: Use discard at 100% hydration (equal parts flour and water by weight). If your starter has a different consistency, you might need to adjust your liquids. For a sourdough-free version, try this lemon sheet cake.

Lemon zest: Most of your lemon flavor comes from the zest, not the juice. Zest your lemons before juicing them, avoiding the bitter white pith.

13×9 baking pan: This size gives you the perfect thickness. A metal pan will give more even baking than glass or ceramic.

Stand mixer or hand mixer: The egg and sugar mixture needs to be beaten until very light and fluffy – much easier with electric help.

Heart’s Content Farmhouse is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. This means that when you click on certain links on this site and make a purchase, I may earn a small commission at no additional cost to you. I only recommend products I genuinely believe in and would use in my own kitchen. As an Amazon Associate, I earn from qualifying purchases.

Lemon Zester Grater, Citrus Zester Grater with Handle, Kitchen Gadgets for Cheese, Lemon, Chocolate, Nutmeg, Ginger, Fruit, Vegetable, Stainless Steel Micro Cheese Grate, Dishwasher Safe(Narrow)Nordic Ware Naturals Aluminum NonStick 9×13-Inches Cake Pan,Silver DII Lemon Bliss Kitchen Collection, Dishtowel Set, 4 Count Shugar Soapworks Oatmeal & Lemon Verbena Soap 6.25 Oz – Plant Based, Vegan, Natural, Pure, No Dyes, Sulfate & Paraben Free (2 Pack)VIVIRBIEN Wood Glass Cake Stand with Dome, 2-in-1 Magnetic Cake Stand with Lid-Multifunctional Cake Plate with Cover for Birthday/Kitchen/Party/Charcuterie Board 11IN Silicone Spatula, Spatula Set Frosting Spatula Optional Size with Space – Saving Design for Baking, Cooking, and Decorating (Large + small yellow)

Make It Your Own

Change the citrus: Try lime or orange instead of lemon.
Add fruit: Fold in 1 cup of fresh blueberries or raspberries. For fall or winter, I love to use apples for a sourdough apple cake.
Different frosting: Cream cheese frosting works well with lemon cake if you prefer something less sweet.
Make a layer cake: Divide the batter between two 9-inch round pans for special occasions. Reduce baking time to about 25 minutes.
No stand mixer? A hand mixer works fine, or energetic whisking by hand if you’re up for it.

Storage & Serving

Serve at room temperature for the best flavor and texture. Serve with berries, whipped cream or vanilla ice cream, and a glass of blackberry lemon water.

This cake stays fresh for up to a week in an airtight container in the refrigerator. The sourdough helps retain moisture, preventing it from drying out.
You can bake the cake up to two days before serving and frost it the day of. The unfrosted cake freezes well – wrap tightly and freeze for up to three months.

This cake is a practical way to use up discard while making something that everyone will enjoy. It’s perfect for a family dessert, a birthday, or bringing to a potluck. Hope you love it. ❤️

Sourdough Discard Lemon Sheet Cake