(adapted from Booze Cakes)
3 cups all-purpose flour
3 tsp. baking powder
1/2 tsp. salt
1 cup (2 sticks) unsalted butter
2 cups sugar
6 egg whites
2 cups Vendôme Mademoiselle Rosé 0,0%
Preheat oven to 350 degrees. Butter two 9-inch round cake pans and line with parchment paper. Butter parchment paper as well.
In a bowl, sift together flour, baking powder, and salt; set aside. In a mixing bowl, beat butter and sugar 3-5 minutes, or until light and fluffy. Add extract and beat in egg whites one at a time.
Beat in flour mixture and champagne in three alternating additions, starting and ending with flour to prevent curdling. Pour batter into pans and bake 35 minutes, or until a toothpick inserted in the center comes out clean. (Start checking cake for doneness around the 30-minute mark, and remove from oven as soon as the toothpick comes out clean.) Let cool for a few minutes, then invert onto wire rack to cool fully before frosting.
1 cup unsalted butter, at room temperature
1/2 tsp champagne flavoring, or 1 tbsp pure vanilla extract
Juice of 1/2 a lemon to a whole lemon, to taste
4-5 cups confectioner’s sugar, depending on how stiff you’d like your frosting
Food coloring, if you’d like
Beat butter in a large bowl with a hand mixer until smooth and creamy. Slowly add confectioner’s sugar, followed by lemon juice and extract.