Place 5 cups chopped rhubarb in 9x13 inch pan. May use canned fruit instead. Sprinkle 1 cup sugar, 1 (3 oz.) package of Jello (in complementary flavor), 3 cups miniature marshmallows over rhubarb. Mix a white cake (scratch or mix) and pour over all. Bake at 350 degrees for 55 minutes. Serve with ice cream or Cool Whip.