Preheat oven to 350F and grease a 15x10 jelly roll pan, so the batter releases easily after baking. Use a light, even coating across the bottom and sides.

Whisk all-purpose flour, baking powder, baking soda, pumpkin pie spice, cinnamon, and salt in a bowl until the mixture is evenly combined. Keep whisking until no dry streaks remain.

Beat eggs, granulated sugar, vegetable oil, pumpkin puree, and vanilla extract until smooth, with no visible sugar lumps. Stop once the batter looks uniform and glossy.

Fold the flour mixture into the pumpkin mixture until just combined, avoiding overmixing for a tender crumb. The batter should look thick and cohesive with no large flour patches.

Pour the batter into the prepared pan and spread into an even layer. Tap the pan lightly to settle the surface.

Bake at 350F for 25-30 minutes, until a toothpick inserted in the center comes out clean. The top should look set and lightly golden.

Cool the bars completely before frosting to prevent the frosting from melting. Let them rest until fully room temperature.

Beat cream cheese and unsalted butter until smooth and creamy. Mix until no lumps remain.

Add powdered sugar, vanilla, and cinnamon, then beat until the frosting is smooth and fluffy. Stop when it holds soft peaks.

Spread the frosting over the cooled bars in an even layer, then swirl the top if desired. Cover to the edges for a neat finish.

Dust with cinnamon for a spiced top layer. Use a light, even shake so it doesn’t clump.

Refrigerate for 30 minutes before cutting into bars. Chill until the frosting firms up for clean slices.