Set your oven to 350°F (175°C) and prepare three 8-inch round cake pans by greasing, flouring, and lining with parchment.
Beat the butter until smooth and creamy.
Add sugar, oil, and vanilla extract. Mix well until creamy.
In a separate bowl, whisk together flour, baking powder, and salt.
Add flour and buttermilk in alternating additions, followed by flour and pink champagne.
Stir in pink coloring if using.
In a clean bowl, beat egg whites until stiff peaks form.
Gently fold egg whites into the batter until fully combined.
Pour evenly into pans and bake 25–28 minutes until a toothpick comes out clean.
Let cakes cool in the pans 10–15 minutes, then turn out and cool completely.
Simmer 2 ¼ cups pink champagne in a pan until reduced to 6 tablespoons. Cool completely.
Beat butter until smooth, gradually add powdered sugar, then vanilla extract. Slowly mix in cooled reduction until fluffy.
Level cake layers if needed. Layer with frosting, cover the sides, and decorate as desired.
