Rhubarb Upside-Down Cake
["2 Tbsp. butter", "1 c. brown sugar", "1 c. sugar", "3/4 c. shortening", "1 egg", "2 c. sifted flour", "2 1/2 tsp. baking powder", "1/2 tsp. salt", "2 c. diced rhubarb", "1 c. milk"]
["In an ovenproof skillet or heavy pan, melt 2 tablespoons butter.", "Stir in brown sugar and diced rhubarb.", "Cream sugar and shortening.", "Beat in egg.", "Sift together flour, baking powder and salt.", "Add dry ingredients to creamed mixture alternately with milk.", "Pour batter over rhubarb and bake at 375\u00b0 for 40 to 45 minutes.", "Turn upside-down on plate.", "Serve with cream or milk."]
["butter", "brown sugar", "sugar", "shortening", "egg", "flour", "baking powder", "salt", "rhubarb", "milk"]