Preheat oven to 350°F / 175°C. Line four 7-inch or three 8-inch pans with parchment rounds and grease with non-stick baking spray.

Mix cake flour, granulated sugar, baking powder, and salt together in a stand mixer or hand mixer until fully combined.

Slowly mix in room temperature unsalted butter until no large chunks remain and the mixture looks like moist sand.

Pour in egg whites and mix on low until just incorporated. Scrape the sides and bottom of the bowl as needed.

Mix in buttermilk, vegetable oil, and vanilla extract on low speed until fully incorporated. Beat on medium speed for about 30 seconds.

Divide the batter for coloring: pour half into a separate bowl to color one light pink and the other a deeper shade of pink. Divide evenly between prepared pans.

Bake for 33-37 minutes or until a toothpick comes out with a few moist crumbs, rotating pans halfway through.

Let the pans cool for 10 minutes, then run a spatula around the perimeter to separate the cake from the pan. Freeze layers for 30 minutes.

Level the tops of the cooled cake layers with a serrated knife. Optionally torte the layers horizontally.

For the buttercream frosting, beat unsalted butter and cream cheese until smooth. Mix in vanilla extract and salt.

Gradually mix in powdered sugar and heavy cream until desired consistency is reached.

For assembly, stack and frost cake layers on a cake board with a dab of frosting, spreading an even layer between each layer.

Apply a thin coat of frosting around the cake to fully cover. Chill until firm to the touch.

Apply a thicker layer of frosting and smooth the sides. Color remaining buttercream in shades of pink.

Pipe hearts and details around the cake using the colored frosting.