Step 1

Preheat oven to 350F. Lightly grease one 6-inch round cake pan then line the bottom with parchment paper.

Step 2

In a medium bowl, sift together the flour and cornstarch then stir in baking soda and salt.

Step 3

In a large mixing bowl (with the paddle attachment if using a stand mixer), beat together the butter, sugar, and lemon zest until light and creamy, about 1-2 minutes.

Step 4

Scrape down the bowl then beat in the egg for 1 minute.

Step 5

Add the flour mixture alternately with the buttermilk, adding the flour in 3 additions and the milk in 2 additions (begin and end with dry ingredients). Add the lemon juice.

Step 6

Transfer the batter to the pan. Bake 25-30 minutes or until a toothpick inserted in the middle comes out clean. Cool for about 15 minutes, run a knife along the edge of the pan to loosen, and invert onto a cooling rack. Cool right-side-up.

Step 7

Decorate with frosting of choice.Cover and store the frosted cake at room temperature for up to 2 days (buttercream only) or in the refrigerator for up to 1 week (buttercream and cream cheese). For best results, let the refrigerated cake sit at room temperature 15-30 minutes before serving.