Preheat oven to 350°F (175°C) and grease a 9x13 inch baking pan. In a large bowl, whisk together the flour, baking powder, baking soda, cinnamon, ginger, nutmeg, and salt.

In a separate bowl, beat the granulated sugar, brown sugar, oil, and eggs until well combined. Stir in the pumpkin puree.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Spread the batter evenly into the prepared baking pan.

Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean. Let the bars cool completely on a wire rack before frosting.

In a medium bowl, beat the softened cream cheese and butter with an electric mixer until smooth and creamy.

Gradually add the sifted powdered sugar, vanilla extract, and a pinch of salt. Beat on low speed until combined, then increase to high and beat until light and fluffy.

Once the pumpkin bars are completely cool, spread the cream cheese frosting evenly over the top. Cut into squares and serve.