1. Preheat oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan. 2. In a large bowl, whisk together the melted butter and granulated sugar until well combined. 3. Beat in the eggs one at a time, then stir in the vanilla extract. 4. In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix. 5. In a small bowl, combine the pumpkin puree and pumpkin pie spice. 6. Pour about two-thirds of the brownie batter into the prepared pan and spread evenly. Drop spoonfuls of the spiced pumpkin mixture over the batter. Top with the remaining one-third of brownie batter. 7. Using a knife or skewer, swirl the pumpkin mixture into the brownie batter to create a marbled effect. 8. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs. Do not overbake. 9. Let cool completely in the pan on a wire rack before cutting into squares. Enjoy your delicious Pumpkin Patch Brownies!