Preheat the oven to 325°F (163°C). Grease three 8-inch cake pans with cooking spray and line the bottoms and sides with parchment paper. Soak three cake baking strips in water.

Sift the flour, baking powder, baking soda, and salt into the bowl of a stand mixer, then stir in the sugar.

In a separate bowl, whisk together the buttermilk, melted butter, vegetable oil, eggs, vanilla extract, vinegar, and pink food coloring.

Gradually add the wet ingredients to the dry ingredients in the stand mixer, using the paddle attachment. Mix until just combined, being careful not to overmix.

Divide the batter evenly between the three prepared pans. Squeeze out any excess water from the baking strips and wrap them around the pans.

Bake for 50-55 minutes, or until the cakes are springy to the touch and a toothpick comes out clean or with a few crumbs attached.

Let the cakes cool in the pans for 20 minutes before inverting them onto a cooling rack. Remove the parchment and allow the cakes to cool completely.

Fill a pot halfway with water and bring it to a simmer. Place a heatproof bowl with the egg whites and granulated sugar over the pot of simmering water, whisking to combine. Continue to heat, whisking frequently, until the mixture reaches 160°F (71°C) and whisk for an additional 2 minutes to ensure the egg whites are safe to consume.

Transfer the mixture to the bowl of a stand mixer fitted with the whisk attachment. Whisk on high speed for about 10 minutes until soft peaks form, and the mixture resembles meringue.

Switch the mixer to the paddle attachment and reduce the speed. Gradually add the softened butter, a few cubes at a time. Initially, the mixture may look curdled, but continue mixing until it turns into a smooth, silky buttercream.

To add color, use a toothpick to add small amounts of pink food coloring, mixing after each addition. The frosting should be slightly lighter than the cake layers for contrast. For the best results, use the frosting immediately.

Set aside 1 cup of frosting for piping rosettes.

Trim the top and bottom of each cake layer using a large serrated knife or a cake leveler to remove any crust and create even, flat layers.

Attach an 8-inch cake board to a 10-inch cake board with a little buttercream. Place the cake board on a cake turntable, then set the first cake layer on top with a small amount of buttercream to help it stick.

Pipe a thin layer of frosting over the first cake layer, smoothing it with a cake scraper if needed, then add the second layer on top. Repeat this process with more frosting, then add the third layer.

Trim the sides of the assembled cake using a serrated knife to create a flat, even surface.

Apply a thin crumb coat of buttercream using an offset spatula. Chill the cake for 15-20 minutes to set the crumb coat.

Add more buttercream to the top and sides of the cake, smoothing it with a cake scraper to achieve a smooth finish. Chilling the cake between frosting steps will help ease this process.

Press pink sprinkles into the side of the cake, focusing on the bottom half. Run a cake smoother around the base to help flatten the sprinkles into the sides. Chill until firm.

Fit a large piping bag with a closed star nozzle and fill it with the reserved frosting.

Pipe 12 rosettes around the top edge of the cake. Sprinkle a few additional sprinkles on top of each rosette.

Carefully transfer the finished cake to a cake stand for serving.