Preheat your oven to 350°F (175°C).

Grease and flour your two 9-inch round cake pans.

In a mixing bowl, whisk together the flour, baking powder, and salt.

In another bowl, beat the softened butter and sugar together until light and fluffy.

Add the egg whites and vanilla extract to the butter mixture and beat until well combined.

Gradually add the dry ingredients to the butter mixture, alternating with the milk.

Divide the batter evenly between the prepared pans.

Bake in the preheated oven for 25 to 30 minutes or until a toothpick inserted in the center comes out clean.

Let the cakes cool in the pans for 10 minutes before transferring them to a cooling rack.