Preheat oven to 350F and grease and flour three 6" cake rounds, line with parchment.
In a medium bowl, whisk flour, baking powder, and salt. Set aside.
Using a stand mixer fitted with the paddle attachment, beat butter until smooth. Add sugar and beat on med-high until pale and fluffy (2-3mins).
Reduce speed and add egg whites one at a time, fully incorporating after each addition. Add vanilla.
Alternate adding flour mixture and champagne, beginning and ending with flour (3 additions of flour and 2 of champagne). Fully incorporating after each addition.
Add a small amount of Fuschia color gel using a toothpick. Mix to incorporate but try not to overmix.
Spread batter evenly into prepared pans. Smooth the tops with a spatula.
Bake for approx. 35 mins or until a toothpick inserted into the center comes out mostly clean.
Place cakes on wire rack to cool for 10mins then turn out onto wire rack to cool completely.