Preheat oven to 350°F. Lightly grease two 8-inch round pans with baking spray or butter and flour, then line the bottoms with parchment paper.

In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large mixing bowl with a hand mixer or stand mixer fitted with the paddle attachment, beat the butter on medium speed until creamy, about 30 seconds. Add the sugar and beat until light and fluffy, about 3 minutes.

Add the egg whites, one at a time, mixing until incorporated well before adding the next. Stop and scrape the bowl down occasionally. Add the extracts and beat until fluffy, about 30 seconds.

With the mixer on low, add a third of the flour mixture followed by half of the milk. Repeat with another third of the flour, the remaining milk, finally ending with the remaining flour. Scrape down the bowl and ensure the batter is well mixed. Divide the batter among the prepared cake pans.

Bake for 35 to 40 minutes or until the centers spring back when gently pressed. Let the cakes cool completely in the pans set on wire cooling racks. Once cooled, invert the cakes onto the racks and remove the parchment paper.

In a large mixing bowl with a hand mixer or stand mixer fitted with the paddle attachment, beat the butter and salt on medium speed until very soft and smooth, about 2 minutes.

With the mixer on low speed, gradually add in the confectioners’ sugar. Scrape the bowl down occasionally. Beat in the vanilla. Slowly beat in 1 tablespoon of milk and continue beating on medium-low speed adding more milk as needed until the texture is smooth and fluffy, about 2 to 3 minutes.

Place one cool cake layer top-side up on a cake stand. Spread 1 cup of frosting over the top of the cake all the way to the edge. Top with the other cake layer, placing it bottom-side up.

Spread the remaining frosting all over the top and sides of the cake. If desired, you can reserve ½ cup of frosting to pipe decoration onto the cake.