Preheat your oven to 350°F (175°C). Grease a 15×10-inch jelly roll pan.
In a large bowl, whisk together flour, sugar, baking powder, baking soda, cinnamon and salt.
In another bowl, combine the butter, eggs, and pumpkin puree. Beat until smooth and well mixed.
Pour the wet ingredients into the dry and stir until just combined—don’t overmix!
Spread the batter evenly into your prepared pan. Bake for 25-32 minutes, or until a toothpick inserted in the center comes out clean. Let the bars cool completely.
In a medium bowl, beat cream cheese, butter, and a pinch of salt until creamy. Gradually add powdered sugar and vanilla, mixing until smooth and fluffy.
Spread the frosting over the cooled pumpkin bars. Sprinkle with a little cinnamon (optional), then cut into 24 squares.
Pan Size: A 15x10-inch jelly roll pan yields a thinner, quicker-baking bar. For a 14.25x9.88-inch jelly roll pan, check for doneness at 25–32 minutes due to slightly thicker batter. See “Half Sheet Pan Variation” below for 18×13-inch pan details.
Yield: Cutting into 2x2.5-inch pieces gives 15–18 bars for a jelly roll pan; adjust size for smaller or larger portions.
Half Sheet Pan Variation: For an 18x13-inch half sheet pan, use the ingredient quantities in parentheses. Spread batter evenly and bake for 30–35 minutes, or until a toothpick comes out clean. Makes about 30 bars (2x3-inch pieces). Frosting will cover the larger surface area.