Preheat your oven to 350°F (175°C). Grease and line a 9x13-inch baking pan with parchment paper for easy removal.
In a medium saucepan, melt the butter over medium heat. Cook for about 5-7 minutes, stirring frequently, until the butter turns golden brown and has a nutty aroma. Remove from heat and let it cool slightly.
In a mixing bowl, combine the brown sugar, granulated sugar, and pumpkin puree. Mix until well combined.
Whisk in the eggs, one at a time, followed by the vanilla extract until the mixture is smooth.
Slowly pour the browned butter into the pumpkin mixture, whisking constantly to combine.
In a separate bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. Be careful not to overmix.
If you’re using white chocolate chips or nuts, gently fold them into the batter.
Pour the batter into the prepared baking pan, spreading it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the blondies to cool in the pan for about 10 minutes before transferring them to a wire rack to cool completely.
Cut into 12 pieces and serve.