Line and grease your cake pans to prevent sticking.
In a bowl, combine the all-purpose flour, baking powder, and salt.
In a separate bowl, beat the butter and sugar together until light and fluffy.
Gradually mix in the egg whites and vanilla extract until fully incorporated.
Add the dry ingredients and champagne in stages, mixing gently after each addition until combined. Add food coloring if using.
Divide the batter evenly between pans and bake until lightly golden and set.
Beat the butter until smooth, then gradually add powdered sugar and reduced champagne. Mix until creamy and fluffy. Add salt, vanilla, and food coloring if desired.
Layer the cake, spread frosting between layers and over the top, then decorate as desired.