Pumpkin Upside-Down Cake

1 pkg. yellow cake mix
1/2 c. sugar
1 (15 oz.) can pumpkin
2 eggs
1 can sweetened condensed milk
2 tsp. pumpkin pie spice
Whipped cream or topping

Mix cake mix according to package directions. Pour into greased 9-inch x 13-inch baking pan. Beat together pumpkin, sugar, milk, eggs and spice. Pour over cake batter evenly. Bake at 350° for 40 minutes. Let stand for five minutes and invert onto a serving tray. When cold cut into squares and top with whipped cream or whipped topping. If whipping cream use one pint, adding a little powdered sugar and vanilla to flavor.