Prep and Preheat: Start by preheating your oven to 350°F (175°C). Grease and line a 9×13 inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.

Combine Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, pumpkin pie spice, and salt. This ensures the leavening and spices are evenly distributed.

Mix Wet Ingredients: In a large bowl, whisk the eggs until frothy. Add the pumpkin puree, vegetable oil, brown sugar, and granulated sugar. Whisk until the mixture is completely smooth and well combined.

Combine Wet and Dry: Add the dry ingredient mixture to the wet ingredients. Use a spatula to fold everything together until just combined. Be careful not to overmix; a few streaks of flour are okay.

Bake to Perfection: Pour the batter into your prepared pan and spread it evenly. Bake for 25-30 minutes, or until the edges pull away from the pan and a toothpick inserted into the center comes out clean.

Cool Completely: Let the bars cool completely in the pan set on a wire rack. This is crucial before frosting.

Make the Frosting: While the bars cool, make the frosting. In a medium bowl, beat the softened cream cheese and butter together until smooth and creamy. Gradually add the powdered sugar and vanilla extract, beating until the frosting is light and fluffy.

Frost and Serve: Once the bars are completely cool, spread the frosting evenly over the top. Lift the bars out of the pan using the parchment paper and slice into squares.