Preheat oven to 350°. Grease and lightly flour two 9-inch round cake pans*; set aside.
Beat cake mix, pumpkin, Hellmann's® or Best Foods® Real Mayonnaise, eggs and pumpkin pie spice in large bowl with electric mixer on low speed 30 seconds. Beat on medium speed, scraping sides occasionally, 2 minutes. Pour batter into prepared pans.
Bake 28 minutes or until toothpick inserted in centers comes out clean. On wire rack, cool 10 minutes; remove from pans and cool completely. Sprinkle, if desired, with confectioners sugar or fill and frost with vanilla frosting.