Preheat your oven to 350°F (175°C).

Grease a 9x13 inch baking pan.

In a large mixing bowl, combine the pumpkin puree, granulated sugar, brown sugar, and vegetable oil.

Beat in the eggs one at a time, mixing well after each addition.

In another bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.

Gradually add the dry ingredients to the pumpkin mixture, stirring until just combined.

Pour the batter into the prepared baking pan, spreading it evenly.

Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.

Allow the bars to cool completely in the pan.

Prepare the cream cheese frosting by beating together the cream cheese, butter, and powdered sugar until smooth.