Rhubarb Upside-Down Cake
["3 c. uncooked rhubarb, chopped", "20 marshmallows, halved", "1 c. sugar", "1 (9 oz.) cake mix"]
["Combine rhubarb, marshmallows and sugar.", "Put in buttered 8 x 8-inch pan.", "Prepare cake mix according to package directions. Pour over rhubarb mixture.", "Bake at 350\u00b0 for 40 to 50 minutes. Yields 8 servings."]
["rhubarb", "marshmallows", "sugar", "cake mix"]