Instructions:

Begin by preheating your oven to 335°F and preparing two 9-inch round cake pans with grease and flour.

In a large bowl, whisk together the cake flour, sugar, salt, baking powder, and baking soda.

Add the egg whites, vegetable oil, buttermilk, softened butter, and vanilla. Mix until the batter is smooth.

Evenly distribute the batter between the two pans.

Bake for about 35 minutes, or until a toothpick comes out clean from the center.

Allow the cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

For the Frosting:

In a saucepan, whisk together the sugar and flour.

Gradually add milk, whisking constantly to avoid lumps.

Cook over medium heat until it thickens to a pudding-like consistency, then cool to room temperature.