Preheat oven to 350ºF.

Prepare an 8x8-inch pan by lining it with parchment paper.

Place butter in a small saucepan over medium low heat. Stir with a silicone spatula often. Bubbles will begin to form and slowly get smaller. The butter will also take on a darker color and you will see small floating brown bits. This will take a total of 10-15 minutes. Remove from heat.

Add cocoa powder and vanilla to browned butter. Whisk until smooth.

In a medium mixing bowl, beat brown sugar and eggs together until light and fluffy.

Pour butter mixture into egg mixture and beat well.

Add flour and salt and beat again until smooth.

OPTIONAL: Stir in pecans. Reserve some to sprinkle on top.

Transfer batter to your prepared pan. Sprinkle remaining pecans on top.

Bake for 40-45 minutes or until a toothpick comes out clean.