1. Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, leaving some overhang for easy removal later.
2. In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg until evenly combined.
3. In a large bowl, mix the pumpkin puree, sugar, melted butter, egg, and vanilla extract. Use a wooden spoon or electric mixer on low speed until smooth and creamy.
4. Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Be careful not to overmix—this keeps the bars tender.
5. Pour the batter into the prepared pan and spread it evenly with a spatula. It’ll be thick but easy to smooth out.
6. Mix the topping sugar and cinnamon in a small bowl, then sprinkle evenly over the batter.
7. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out mostly clean with just a few moist crumbs. The edges should start to pull away from the pan slightly.
8. Let the bars cool completely in the pan on a wire rack. Once cool, lift them out using the parchment overhang and cut into 12 squares.

From my experience, letting these bars cool fully is key. I learned that the hard way during one of my early recipe tests when I sliced them too soon—the texture just wasn’t right. Patience here rewards you with bars that hold together beautifully, perfect for sharing.