Preheat oven to 350° F. Line a 9x13-inch baking dish with parchment paper. Set aside.
Pour the melted butter and cocoa powder in a large bowl. Using an electric hand-mixer, mix until smooth.
Add the flour and sugar. Beat together, then add eggs and vanilla. Mix until just combined. Don't over mix. (Batter will be thick.)
Pour batter into the prepared baking dish and spread out evenly. Bake 25 to 28 minutes or until toothpick inserted in center comes out mostly clean. Remove from oven and allow to stand for 15 minutes before frosting. You want the brownies slightly warm when you frost them!