Step 1 Heat the oven to 350 degrees. Spread the pecans out on a rimmed baking sheet. Toast the pecans until darkened and aromatic, 6 to 8 minutes, being careful not to burn. Remove and cool; coarsely chop.
Step 2 While the pecans are cooling, brown the butter: Place the butter in a wide pan and heat over medium-low heat until the milk solids are nicely browned and the butter has a toasted, nutty flavor, 4 to 5 minutes. Remove from heat and pour into a mixing bowl. Set aside.
Step 3Prepare your 9-inch by 9-inch baking pan by spraying it with non-stick spray, lining with a piece of parchment paper the size of the bottom of the pan, and then spraying once again to coat the paper and the sides of the pan.
Step 4In a medium bowl, whisk together the flour and salt in a large bowl. In a separate large mixing bowl, whisk together the eggs and vanilla.
Step 5Carefully whisk the sugars in with the warm butter, mixing well to combine. Slowly whisk the butter mixture into the beaten eggs and vanilla, mixing well until fully incorporated.
Step 6Add the flour mixture and blend it in until there are just a few pockets of dry flour remaining, careful not to overmix. Add the pecans and fold them in.
Step 7Pour the batter into the prepared pan. Bake the blondies for 12 minutes, then rotate the pan. The blondies will be done when the top is glossy and crackling a little, and the center of the blondies feel slightly firm when pressed gently on top, another 20 to 25 minutes. They will be somewhat soft, but not gooey in the center. Remove from heat and cool on a rack. While the blondies are baking, prepare the glaze.