Prepare the Pumpkin Bars

1. Preheat Oven: Begin by preheating your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan, or line it with parchment paper for easy removal.
2. Mix the Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, allspice, and salt. Set this aside.
3. Combine the Wet Ingredients: In a large bowl, beat together the vegetable oil and granulated sugar until smooth. Add the eggs, one at a time, beating well after each addition. Stir in the pumpkin and vanilla extract, mixing until fully combined.
4. Add the Dry Ingredients: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix, or the bars could become dense.
5. Bake: Pour the batter into your prepared pan and smooth it out evenly. Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean.
6. Cool: Allow the bars to cool in the pan for 10 minutes before transferring them to a wire rack to cool completely.

Prepare the Cream Cheese Frosting

1. Cream the Cheese and Butter: In a medium bowl, beat the cream cheese and butter together until light and fluffy.
2. Add Sugar and Vanilla: Gradually add the powdered sugar, a little at a time, until the frosting is smooth and creamy. Stir in the vanilla extract and a pinch of salt.
3. Frost the Bars: Once the bars have cooled completely, spread the cream cheese frosting evenly over the top.