Preheat your oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper, allowing it to hang over the edges.

In a saucepan over medium heat, melt the unsalted butter, stirring constantly for 5-7 minutes until golden brown and nutty.

In a large mixing bowl, combine the cooled brown butter and brown sugar, beating until well combined. Add the eggs one at a time, followed by the vanilla extract, mixing until smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually mix this into the wet ingredients until just combined.

Gently fold in the chopped pecans using a spatula, ensuring they are evenly distributed.

Spread the batter into the prepared baking pan and bake for 25-30 minutes until the edges are set and the center is golden but soft.

Remove from the oven and allow the blondies to cool completely in the pan on a wire rack, then lift out and slice into bars.