Preheat oven to 350 degrees. Grease a 9x13 pan with cooking spray
Heat a small saucepan over low heat and add butter. Wait until butter has melted and whisk in the cocoa. Remove from heat and set aside to cool for a few minutes.
In a separate bowl, using a hand mixer, combine granulated sugar, flour and salt. Add the cooled cocoa butter mixture and mix on medium speed until well mixed. Add the eggs and vanilla slowly and mix until well combined.
Spread your brownie mixture evenly over your prepared baking pan. Bake for about 20 minutes until a toothpick inserted only comes out with a few crumbs. (if your oven runs hot, watch carefully so it doesn't over bake)
Let brownies cool completely. This can take anywhere from 30-40 minutes.