Preheat your oven to 350°F (175°C) and line an 8x8 inch baking pan with parchment paper.
In a medium saucepan, melt the unsalted butter over medium heat until golden brown and nutty, about 5 minutes. Remove from heat and let cool slightly.
Whisk in granulated sugar, brown sugar, eggs, and vanilla until well combined.
In another bowl, whisk together flour, cocoa powder, and salt. Gradually fold the dry ingredients into the wet mixture until just combined.
Pour the batter into the prepared pan and smooth the top. Bake for 25-30 minutes or until a toothpick comes out with moist crumbs.
Allow to cool in the pan for at least 10 minutes before cutting into squares.
