Brown the Butter: In a light-colored saucepan over medium heat, melt the unsalted butter. Swirl frequently as it foams and sizzles. After 4 to 5 minutes, golden-brown specks will appear at the bottom and a fragrant nutty aroma will develop. Immediately remove from heat and pour into a heatproof mixing bowl to cool for 10 minutes.

Blot the Pumpkin Puree (The Baker Secret): Spread 0.5 cup pumpkin puree across a double layer of paper towels on a plate. Press firmly with 2 more paper towels on top to absorb excess water. Measure out 1/3 cup of blotted, concentrated pumpkin paste. This eliminates wetness and guarantees a dense, chewy blondie texture.

Prep Oven & Pan: Preheat oven to 350°F (175°C). Line an 8x8-inch metal baking pan with parchment paper, leaving generous overhang on two sides. Lightly mist with nonstick baking spray.

Whisk Wet Ingredients: Whisk the dark brown sugar and granulated sugar vigorously into the warm browned butter until smooth and glossy. Whisk in the blotted pumpkin puree, egg yolk, and vanilla extract for 1 minute until well incorporated.

Fold in Dry Ingredients & Fold: Add the flour, pumpkin pie spice, cinnamon, sea salt, and baking powder. Gently fold with a rubber spatula just until no flour streaks remain (do not overmix). Fold in 0.5 cup of white chocolate chips and 1/3 cup chopped toasted pecans.

Spread & Crown: Spread the thick batter evenly into the prepared pan using an offset spatula. Scatter the remaining white chocolate chips and pecans across the top, pressing gently into the batter.

Bake to Chewy Perfection: Bake at 350°F (175°C) for 24 to 28 minutes. A toothpick inserted into the center should come out with moist crumbs (not wet batter). Do not overbake! Cool completely in the pan on a wire rack for at least 1.5 hours so the blondies set into their signature fudgy chew before lifting and slicing into 16 squares.