1. Prepare the Cake:
- Preheat your oven to 350°F (175°C). Grease and flour three 6-inch round cake pans, lining the bottoms with parchment paper for easy removal.
- In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
- In a large mixing bowl, beat the butter until smooth. Add the sugar and continue beating on medium-high speed until the mixture becomes pale and fluffy, about 2-3 minutes.
- Reduce the mixer speed and add the egg whites one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract.
- Alternately add the dry ingredients and the pink champagne to the butter mixture, beginning and ending with the dry ingredients. Mix until just combined. If desired, add a few drops of pink food coloring to achieve a light pink hue.
- Divide the batter evenly among the prepared cake pans. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
- Allow the cakes to cool in their pans for about 10 minutes before transferring them to a wire rack to cool completely.
2. Prepare the Champagne Reduction:
- In a small saucepan, bring the ½ cup of pink champagne to a simmer over medium heat. Let it reduce to approximately ¼ cup. Once reduced, remove from heat and allow it to cool completely before using in the frosting.
3. Make the Champagne Buttercream Frosting:
- In a large mixing bowl, beat the room temperature butter until it becomes creamy and light.
- Gradually add the powdered sugar, one cup at a time, mixing well after each addition.
- Pour in the cooled champagne reduction, vanilla extract, and a pinch of salt. Continue to beat the mixture until it becomes light and fluffy. If desired, add a few drops of pink food coloring to achieve a soft pink shade.
4. Assemble the Cake:
- Once the cake layers have completely cooled, place one layer on your serving plate or cake stand. Spread a generous amount of the champagne buttercream frosting over the top.
- Place the second cake layer on top and repeat the frosting process. Add the third layer and frost the top and sides of the cake with the remaining buttercream, smoothing it out for a polished finish.
- For an elegant touch, consider decorating the cake with edible pearls, sprinkles, or a light dusting of edible glitter.