Lemon Sheet Cake with Buttercream Frosting

1. Prepare Baking Pan and Preheat Oven

Begin by preheating your oven to the temperature specified for your cake. Generously grease a 9-by-13-inch baking pan with butter and lightly dust it with flour, shaking out the excess. Alternatively, you can line the pan with parchment paper for easy removal later on.

2. Create Milk Mixture

In a small jug, stir together the whole milk and fresh lemon juice. The acidity of the lemon juice will slightly curdle the milk, creating a homemade buttermilk that contributes to the cake's tender texture.

3. Combine Dry Ingredients

In a medium bowl, sift together the all-purpose flour, baking powder, baking soda, and kosher salt. This dry mix will ensure an even rise and a perfectly structured cake.

4. Cream Butter, Sugar, and Zest

The most crucial step in creating a light and fluffy cake is to cream together the softened butter, granulated sugar, and lemon zest until the mixture is pale and voluminous. This process introduces air into the batter, which will help the cake rise beautifully. Once creamed, add the eggs one at a time, ensuring each is fully incorporated before adding the next.

5. Combine Wet and Dry Ingredients

With your mixer on a low speed, alternately add the dry ingredients and the milk mixture to the creamed butter, beginning and ending with the dry ingredients. This alternating method helps maintain the structure of the batter and prevents over-mixing, which can lead to a denser cake.

6. Bake the Cake

Pour the batter into the prepared pan and smooth the top with a spatula. Bake in the preheated oven until the cake is golden and a tester inserted into the center comes out clean, about 35 to 40 minutes.

7. Cool the Cake

Once baked, let the cake cool in the pan on a wire rack until completely cooled. Patience is key here, as a cool cake will hold up better under the frosting and prevent it from melting.

8. Prepare the Frosting

For the frosting, beat the softened butter with the confectioners’ sugar, lemon zest, and a pinch of salt until smooth. Gradually add lemon juice until you reach the desired consistency, keeping in mind that the tang of the lemon should complement the sweetness of the sugar.

9. Frost the Cake

When the cake is cool, spread the lemon buttercream frosting evenly over the top with a spatula or knife. The frosting should be lusciously smooth and inviting, a perfect match for the zesty cake beneath.