Preheat oven to 350 degrees and line an 8-inch by 8-inch baking pan with parchment paper.
In a medium bowl, whisk together the flour, baking powder, cornstarch, and salt. Set aside.
In a separate bowl, beat together the butter and brown sugar until smooth and creamy.
Add the egg and vanilla and beat to combine.
Mix in the dry ingredients until well mixed.
Separate half the batter into a different bowl and add the pumpkin, pumpkin pie spice, and cinnamon. Mix to combine.
In the other bowl, fold in the chocolate chips.
Spoon each batter into the lined baking dish, alternating between pumpkin batter and chocolate chip batter. Then, use a flat spatula to smooth the batter into the pan.
Bake in the preheated oven for 25 to 30 minutes, until a toothpick inserted into the center comes out clean.
Allow the blondies to cool completely in the pan, then remove them from the pan and cut them into 9 bars before serving.