Preheat oven to 350°F. Grease and line two 8-inch round cake pans. Whisk flour, baking powder, and salt. Cream 1 cup butter and sugar until fluffy. Add eggs one at a time, then vanilla. Alternate adding dry ingredients and milk, starting and ending with dry. Divide batter between pans, bake 22-25 minutes until a toothpick comes out clean. Cool completely.

Beat 1 1/2 cups butter until creamy. Gradually add 4 1/2 cups powdered sugar, 2 tbsp milk, and 2 tsp vanilla. Remove 1/2 cup plain buttercream and set aside. Tint the large batch golden with yellow and a tiny dab of orange gel. In the reserved portion, beat in the remaining 1/4 cup butter, 1 cup powdered sugar, 1/4 cup cocoa, and enough milk to make a thick, pipable chocolate frosting.

Level cake layers if needed. Place one layer on a plate, spread with golden buttercream, and top with the second layer. Apply a thin crumb coat of golden buttercream over the entire cake. Chill 15 minutes.

Spread the remaining golden buttercream thickly over the cake and smooth the top and sides with a bench scraper.

Transfer the chocolate buttercream to a piping bag fitted with a small round tip. Pipe irregular ovals, clusters, and broken spots all over the cake. Serve.