Melt butter in a 12-inch cast-iron skillet over low heat. Sprinkle evenly with brown sugar. Arrange pear slices over sugar; top with raisins, walnuts, and cherries.
Stir together cake mix, water, and egg until moistened; pour over pears. Bake at 350° for 35 minutes or until a wooden pick inserted in center comes out clean.
Invert immediately onto a serving platter. Cool before serving.
Tip: Make sure pears are well drained before arranging in skillet.