Ingredients
For the Cake
- 1 1/2 cups all-purpose flour
- 2 tablespoons cornstarch
- 2 teaspoons baking powder
- 1 1/2 tablespoons poppy seeds
- 1/4 teaspoon salt
- 1/2 cup + 1 tablespoon unsalted butter, softened
- 3 tablespoons vegetable oil
- 1 cup + 2 tablespoons granulated sugar
- 2 tablespoons lemon zest (from ~1 large lemon)
- 3 large eggs, room temperature
- 1/4 cup milk, room temperature
- 1/4 cup + 2 tablespoons sour cream
- 3 tablespoons fresh lemon juice
For the Cream Cheese Frosting
- 6 tablespoons unsalted butter, softened
- 6 oz cream cheese, softened
- 2 1/4 cups powdered sugar
- 2-3 tablespoons milk
- Lemon curd, for topping (optional)
Make the Cake Batter
Preheat your oven to 350°F. Grease an 8×8 inch baking pan and line the bottom with parchment paper.
In a medium bowl, sift together the all-purpose flour, cornstarch, baking powder, poppy seeds, and salt. Whisk to combine and set it aside.
In a large bowl, combine the granulated sugar and lemon zest. Use your fingers to rub the zest into the sugar until it’s fragrant and slightly damp. This helps release the lemon oils for a more intense flavor.
Add the softened butter and vegetable oil to the sugar mixture. Using a hand or stand mixer on medium speed, cream them together for ~2-3 minutes until the mixture is light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Add the milk, sour cream, and lemon juice. Mix until they are just combined. The batter might look slightly curdled at this point, which is normal.
Add the dry ingredients to the wet ingredients and gently fold with a spatula until just combined.
Be careful not to overmix the batter, as this can lead to a tough cake.
Bake the Cake
Pour the batter into the prepared pan and spread it into an even layer.
Bake for ~25-30 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs attached.
Allow the cake to cool completely in the pan before frosting.
Make the Frosting
In a large bowl, beat the softened butter and cream cheese with a mixer until they are light and creamy.
Add the powdered sugar in three additions, mixing well after each one. Add milk, one tablespoon at a time, until the frosting reaches a smooth, spreadable consistency.
Spread the frosting evenly over the cooled cake.
If you’re using it, add dollops of lemon curd over the frosting and use a knife to gently swirl it in.
Lemon Poppyseed Sheet Cake
Ingredients
For the Cake
- 1 1/2 cups all-purpose flour
- 2 tablespoons cornstarch
- 2 teaspoons baking powder
- 1 1/2 tablespoons poppy seeds
- 1/4 teaspoon salt
- 1/2 cup + 1 tablespoon unsalted butter softened
- 3 tablespoons vegetable oil
- 1 cup + 2 tablespoons granulated sugar
- 2 tablespoons lemon zest from ~1 large lemon
- 3 large eggs room temperature
- 1/4 cup milk room temperature
- 1/4 cup + 2 tablespoons sour cream
- 3 tablespoons fresh lemon juice
For the Cream Cheese Frosting
- 6 tablespoons unsalted butter softened
- 6 oz cream cheese softened
- 2 1/4 cups powdered sugar
- 2-3 tablespoons milk
- Lemon curd optional, for topping
Instructions
- Preheat oven to 350°F. Grease 8×8 inch pan and line bottom with parchment.
- Sift together flour, cornstarch, baking powder, poppy seeds, and salt.
- Rub lemon zest into sugar until fragrant.
- Beat butter, oil, and lemon-sugar mixture until light and fluffy, 2-3 minutes.
- Beat in eggs one at a time.
- Mix in milk, sour cream, and lemon juice until just combined.
- Fold dry ingredients into wet ingredients until just combined.
- Pour batter into pan and bake 25-30 minutes until toothpick comes out clean.
- Cool completely in pan.
- Beat butter and cream cheese until light and creamy.
- Gradually mix in powdered sugar, adding milk until spreadable.
- Spread frosting over cooled cake.
- Optional: Swirl lemon curd into frosting.
