Raspberry and chocolate are a classic pairing, but other flavors of preserves like cherry, for example, are equally luscious in this recipe.
Prepare the batter and spread in the greased baking pan. Spoon seedless raspberry preserves at even intervals across the surface.
Insert a small metal spatula or knife in the center of one spoonful of preserves. Drag through the preserves with a swirling motion to pull them through the batter until you reach another dollop of preserves. Continue swirling the remaining preserves to create a marbleized pattern.
Spread frosting evenly over the entire surface of the batter. Using just enough pressure to make score marks, pull the tines of a fork through the frosting on the diagonal.