Preheat the oven to 350°F. Line an 8-inch square baking pan with parchment paper and set aside.
Add the melted butter and brown sugar to a large mixing bowl. Mix until well combined. Add the pumpkin puree, egg, vanilla extract and salt to the mixing bowl, and mix once again until well combined.
Add the flour, pumpkin pie spice and baking powder. Mix until just combined. Fold in the chocolate chips.
Transfer the batter to the prepared baking pan. Bake for 35 minutes, or until just cooked through. Allow to cool completely in the tin before slicing into squares.
Notes
The baking pan can be sprayed with non-stick cooking spray instead of lining with parchment paper.
The center of the blondie should still be slightly soft once baked. An inserted skewer or toothpick should come out mostly clean.
Extra chocolate chips can be sprinkled over the batter just before baking.
Storage:Store these blondies in an airtight container at room temperature for up to 3 days. These blondies are suitable for freezing. Freeze in an airtight container for up to 3 months. Thaw at room temperature before enjoying.