Preheat the oven to 350°F. Spray a 13-by-18-inch rimmed baking sheet with cooking spray.

Whisk together the flour, baking powder, baking soda, and salt in a medium bowl.

In a large bowl, combine the granulated sugar and lemon zest and work the zest into the sugar with your fingers.

Add the eggs to the sugar mixture and whisk until foamy and lighter in color, 1 to 2 minutes.

Whisk in the vegetable oil, vanilla extract, lemon extract, and lemon juice.

Gradually stir in the flour mixture, alternating with the buttermilk, whisking well after each addition.

Transfer the batter to the prepared pan. Bake until the cake is lightly golden and a toothpick inserted into the center comes out clean, 16 to 18 minutes, rotating the pan halfway through.

Let cool completely in the pan on a rack, at least 1 hour.

Beat the butter in a stand mixer fitted with the paddle attachment until creamy.