Lemon Sheet Cake With Buttercream Frosting

Step 1

Make the cake: Heat oven to 350 degrees. Line a 9-by-13-inch baking pan with parchment paper, butter and flour the paper.

Step 2

In a measuring cup with a spout, combine the milk and lemon juice. Whisk the flour, baking powder, baking soda and salt together in a medium bowl.

Step 3

In the bowl of a stand mixer fitted with the paddle attachment, cream butter, sugar and lemon zest until light and fluffy, about 5 minutes. Add eggs, one at a time, mixing for about 30 seconds after each. Scrape down bottom and sides of the mixer to ensure the mixture is well combined.

Step 4

With the mixer on low speed, alternately add the flour mixture and milk mixture to the bowl in three additions. Mix until just combined, then use a rubber spatula to finish mixing the batter. Pour the batter into the prepared pan, smooth the top and tap the pan on the counter a few times to release any large air pockets. Bake for 35 to 40 minutes or until puffed and golden and a cake tester inserted into the center comes out clean. Cool the cake completely on a rack before frosting.

Step 5

Meanwhile, prepare the frosting: Combine the butter, confectioners' sugar, lemon zest and a pinch of salt in the bowl of a stand mixer fitted with the paddle attachment. Mix on low until combined, then turn the mixer up to medium-high and stream in 3 tablespoons of lemon juice. Whip the frosting until very light and fluffy, about 5 minutes, adding additional lemon juice as necessary until frosting is smooth and spreadable.

Step 6

Spread the frosting over the cooled cake and serve. Store leftover cake at room temperature, covered for up to 2 days.