Melt butter in a medium saucepan over medium heat. Stir constantly for 5–7 minutes until it foams and turns golden brown with a nutty aroma. Remove from heat and cool slightly.
In a large bowl, combine brown butter (including browned bits), brown sugar, and granulated sugar. Stir until smooth. Add pumpkin puree, eggs, and vanilla extract. Mix until creamy.
In another bowl, whisk together flour, baking powder, baking soda, pumpkin pie spice, and salt. Gradually add to wet mixture, folding gently until just combined.
Stir in white chocolate chips or pecans if using.
Preheat oven to 350°F (175°C). Line a 9x13-inch pan with parchment paper, leaving some overhang.
Spread batter evenly into the pan and bake for 25–30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
Allow blondies to cool in the pan for 15 minutes. Lift out using the parchment paper and place on a wire rack to cool completely. Slice into squares or bars.
Enjoy as-is or top with a drizzle of caramel for an extra sweet finish.
