Preheat the oven to 350°F.
Line 9x13 pan with nonstick foil.
In a small pot, melt the butter and cocoa on low.
Cool 5 mins.
In a mixer, combine sugar, flour, salt.
Add the melted butter/cocoa, beating 2 mins.
Add one egg at a time and then the vanilla.
Spread in the pan and bake 22-25 mins. (Until a tester comes out with a few moist crumbs)
Cool completely.