Cake: Blend cake mix, pumpkin, dressing and eggs with electric mixer on medium speed until well blended. Pour into greased 15x10x1-inch baking pan.
Bake at 350°F for 18 to 20 minutes or until toothpick inserted in center comes out clean. Cool completely on wire rack.
Frosting: Blend all ingredients with electric mixer on low speed until moistened. Beat on high speed until light and fluffy. Spread over cake.
Variation: Pour prepared cake batter into greased 13x9-inch baking pan. Bake at 350°F for 32 to 35 minutes or until toothpick inserted in center comes out clean. Continue as directed.