Step 1

Preheat oven to 350 degrees.

Step 2

Grease and flour two 8 inch cake pans. Set aside.

Step 3

In a large bowl, whisk together the flour, baking powder and salt. Set aside.

Step 4

In the bowl of a stand mixer, beat the butter and sugar together until fluffy. Add the egg whites, one at a time, fully incorporating after each addition. Add the egg and vanilla, mix to combine.

Step 5

Alternate adding the flour mixture and champagne, starting and ending with the flour. Stir in the sour cream until well combined.

Step 6

Add 1-2 drops of Magenta color gel until the desired color is achieved.

Step 7

Divide the batter evenly between the two cake pans and smooth the tops with a spatula.

Step 8

Bake for approximately 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Step 9

Transfer to a wire rack to cool for 10 minutes, then turn the cakes out onto the rack to cool completely.

Step 10

To make the buttercream, add the butter to the bowl of a stand mixer and beat until fluffy.

Step 11

Add vanilla and 1 cup confectioners' sugar beating on medium speed until well combined.

Step 12

Slowly add 1 cup more confectioners' sugar to the frosting and beat until smooth.

Step 13

Turn the mixer to low and stir in the champagne.

Step 14

Begin adding remaining sugar to the frosting one cup at a time at medium speed, beating well until the desired consistency is achieved.

Step 15

Add 1-2 drops color gel if you'd like pink frosting.

Step 16

Transfer to an airtight container and store at room temperature for 2 hours or overnight.

Step 17

To frost the cake, place one cake layer on a cake stand or serving plate.

Step 18

Top with approximately 2/3 cup of frosting. Spread evenly to coat the top and sides of the cake. Place the remaining cake layer on top and apply a thin coat of frosting all over the cake. Chill for 20mins.

Step 19

Top the cake with another 2/3 cup frosting. Smooth the top and sides of the cake with the frosting.

Step 20

Decorate with rosettes and sprinkles, if desired.

Step 21

Serve immediately or chill overnight.