Mix flour (2 cups), baking soda (1 teaspoon), baking powder (2 teaspoons), salt (1/2 teaspoon), cinnamon (1/2 teaspoon), ginger (1/2 teaspoon), cloves (1/2 teaspoon), and nutmeg (1/2 teaspoon) in a small bowl. Set aside.
In a large bowl, beat together eggs (4), oil (1 cup), sugar (2 cups), and pumpkin (1 can). Gradually add the dry ingredients to the egg mixture and blend well.
Pour the batter into an ungreased rimmed baking sheet (half sheet size-17.88 x 12.88 x 1.06) and bake for 15-20 minutes or until a toothpick inserted in the center comes out clean. Let cool completely.
Meanwhile, prepare to frost by beating together all frosting ingredients until smooth. Frost cake. Store in the refrigerator.
Notes
Canned Pumpkin: Be sure you grab canned pumpkin puree, not pumpkin pie mix! Pumpkin pie mix has other ingredients that will throw off the ratio of seasonings in your cake.
Do pumpkin bars with cream cheese frosting need to be refrigerated: All cakes with cream cheese frostings must be refrigerated within 2 hours (including prep time) after making.