FOR THE CAKE-
2 1/2 cups sifted cake flour
1 Tbsp. baking powder
1/2 tsp. table salt
1 1/2 sticks unsalted butter, softened
2 cups granulated sugar
3/4 cup brut sparkling wine
1/4 cup milk
1 tsp. vanilla extract
6 drops red food coloring
6 egg whites
FOR THE FROSTING-
1/2 cup shortening
1/3 cup brut sparkling wine
5 cups sifted powdered sugar
1/2 tsp. unflavored gelatin
1 Tbsp. cold water
3/4 cup heavy cream
Preheat oven to 350 degrees. Line two 9-inch round cake pans with parchment paper and coat with nonstick spray. Sift together flour, baking powder, and salt; set aside.
Cream butter and granulated sugar in a stand mixer until mixture is light and fluffy, about 3 minutes. Combine 3/4 cup sparkling wine, milk, and vanilla.
Add flour and wine mixtures alternately to butter mixture, combining well after each addition. Tint batter with red food coloring.
Beat egg whites in a separate bowl with clean beaters until soft peaks form, about 2 minutes. Fold egg whites into cake batter in thirds, stopping as soon as whites are incorporated. Divide batter evenly between prepared pans.
Bake cakes until a toothpick inserted in the center has only or or two crumbs on it, about 30 minutes. Cool cakes in pans for 10 minutes, then turn cakes out onto a rack to cool completely.
Beat together shortening, 1/3 cup sparkling wine, and powdered sugar for frosting in a bowl until smooth. Spread 1 cup frosting on top of one cooled cake round. Place second cake round on top of the frosted round.
Sprinkle gelatin into water in a small saucepan. Let mixture sit for 5 minutes, then gently warm over low heat until gelatin dissolves. Cool to room temperature.
Beat heavy cream until soft peaks form, about 3 minutes. Add gelatin mixture to cream; continue to beat until stiff peaks form. Working in batches, gently fold whipped cream into remaining frosting.
Spread frosting onto top and sides of cake, being careful not to overwork. Refrigerate cake 1 hour with a large bowl over the top to protect frosting. Use a spatula to gently swirl frosting before serving.
FOR THE CAKE-