Oil and line a 9″ skillet with parchment paper. Drizzle in 1/4 cup melted butter, and layer with sliced pineapple and cherries. Sprinkle chaotically with light brown sugar. Pour in vanilla-flavored sponge cake batter and bake until sides have pulled in from the pan. Cool well before inverting on a plate. Refrigerate before slicing and serving.
