Place the butter and brown sugar in a frying pan and melt until it boils or bubbles. A cast iron pan works well because it's heavy and will be less likely to scorch.
Place pineapples in the butter and sugar mixture. Put cherries in the center of the pineapple. Cut the slices of pineapple into halves and line the sides of the frying pan with them (standing up on edge).
Prepare the yellow cake mix as directed on the box to mix the batter, but do not bake in a separate pan; instead, pour the batter over the pineapple and cherries.
Bake at 350 degrees. When the cake is done, loosen the edges with a butter knife and allow the cake to sit five minutes, then turn it upside down on a serving dish. (It takes 2 people to turn!) Serve with Cool Whip. 10-12 servings.