1. For the Cake:2. Preheat oven to 350°F / 175°C. Grease and flour four 8-inch round cake pans (or bake in batches).3. In a stand mixer, mix cake flour, sugar, baking powder, and salt.4. Slowly add the butter cubes on low speed. Mix until the mixture resembles coarse sand.5. In a separate bowl, whisk egg whites, buttermilk, oil, vinegar, and vanilla.6. On low, slowly add half of the wet mixture to the dry. Increase speed to medium and beat for 2 minutes.7. Scrape the bowl, then on low, add the remaining wet mixture. Mix for 30 seconds.8. Divide the batter evenly into 4 bowls. Leave one white. Tint the other 3 bowls with 1 drop, 3-4 drops, and 6-8 drops of pink gel coloring, respectively.9. Pour each color into a prepared pan. Bake for 18-20 minutes (or 33-37 mins if using 2 pans for thicker layers).10. Let cool in pans for 10 minutes, then invert onto a wire rack to cool completely.11. 12. For the Frosting:13. In a stand mixer, beat the butter and cream cheese until smooth and creamy.14. Add the vanilla and salt, and mix.15. On low speed, slowly add the powdered sugar until fully incorporated.16. Add the heavy cream, then beat on medium-high speed for 3-5 minutes until light and fluffy.17. 18. For Assembly:19. Level the cooled cakes. Place the darkest layer on a cake stand. Top with frosting.20. Add the medium layer, more frosting, the light pink layer, more frosting, and then the white layer.21. Cover the cake in a thin crumb coat, chill for 30 minutes, then frost with the remaining frosting.