Preheat oven to 350 degrees.
In a pot, melt the butter over medium heat on the stove. Add the sugar and cocoa powder and whisk to combine. Remove from heat. Add the vanilla and eggs and continue to whisk until totally incorporated. Add the flour and salt and combine until smooth.
Grease a small baking dish, I used an 8x8 metal pan, and line with parchment paper. Evenly distribute the batter and tap the dish on the counter making sure all the air bubbles are out. Set aside and make the blondie brownie mixture.