For the yellow cake: Use a rectangle half sheet pan (12 x 18 x 2), and double the recipe for "Yellow Cake Layers" from The Modern Baker" by Nick Malgieri.
For the raspberry buttercream: Make 1 1/2 times the recipe for Nick's "Raspberry Buttercream." Before adding the raspberry puree, reserve 2 cups of the plain buttercream frosting.
For chocolate buttercream: Fold 1/4 cup of cooled melted dark chocolate into 1 cup plain butter cream frosting.
For golden buttercream: Mix 3 drops of yellow food dye with 1/2 cup plain buttercream.
For white buttercream: Reserve remaining 1/2 cup plain buttercream.