• Preheat Oven and Prepare Pan: Preheat your oven to 350°F (180°C). Line an 10x15-inch baking pan (jelly roll pan) parchment paper, allowing some overhang for easy removal. Set aside.
• Mix Dry Ingredients: In a large mixing bowl, combine the flour, pumpkin pie spice, baking powder, baking soda, and salt. Whisk until well blended and set aside.
• Mix Wet Ingredients: In another large bowl, whisk together the pumpkin puree, eggs, oil, granulated sugar, and brown sugar until thoroughly mixed.
• Combine: Add the wet ingredients to the dry ingredients and mix until just combined into a thick batter, being careful not to overmix.
• Transfer Batter: Pour the batter into the prepared pan, smoothing the top with a spatula.
• Bake: Bake for 20-22 minutes, or until a toothpick inserted in the center comes out clean and the top is springy to the touch. Allow to cool completely in the pan.

Cream Cheese Frosting

• Sift Ingredients: Sift the powdered sugar and pumpkin pie spice together into a medium bowl. Set aside.
• Cream Base: Using electric beaters, beat the cream cheese and butter in a large bowl until smooth, about 1 minute. Scrape down the sides of the bowl.
• Add Sugar: Gradually add the sifted sugar mixture, beating until the frosting is smooth and creamy.
• Frost Bars: Spread the frosting evenly over the cooled bars. Slice into 2x2-inch squares and serve.