Preheat oven to 350 F.Grease two 8-inch pan and line them with parchment paper.
Cream butter and sugar together in the bowl of a stand mixer, using the paddle attachment. Beat until light and fluffy.
Whisk together flour, cornstarch, salt and baking powder in a large bow.
Gradually add egg whites with the mixer on low to medium speed, mixing until incorporated.
Slowly add milk and almond extract, with the mixer on medium speed.
Add dry ingredients to wet ingredients, 1/3 at a time, with the mixer on low speed.
Pour the batter into the cake pan. Bake for 25-30 minutes until the cakes are golden on top and spring back when pressed. The sides of the cake should begin to pull away from the pan.
Let cakes cool for 10 minutes, then remove from pan and cool on wire rack. Wrap in plastic wrap and freeze at least one hour.