This is one of my very few favorite non-chocolate desserts. I found the recipe in a cookbook from the '70s but changed it a bit.
1 package yellow cake mix
1/3 cup sugar
1/3 cup vegetable oil
1 15 ounce can pumpkin puree
3 teaspoons pumpkin pie spice
Frosting: 1 can vanilla frosting
1 3 ounce package cream cheese, softened
1 teaspoon vanilla
Heat oven to 350 degrees. For bars grease a jelly roll pan, for cake a 13 by 9 inch cake pan. In large mixing bowl, combine sugar, oil, eggs and pumpkin, beat 1 minute on high speed with electric mixer. Add cake mix and spice, beating 2 minutes on high. Pour into prepared ,desired pan. Bake at 350 degrees for 25 to 35 minutes depending on pan size. Cool completely. Beat together frosting, cream cheese and vanilla. Frost cooled bars or cake. Store in refrigerator but bring to room temp. to serve.