Preheat the oven to 350 degrees F. Line your cupcake pan with cupcake liners.
In a large bowl, combine melted butter and sugar. Stir gently and add in eggs and vanilla.
Beat mixture by hand with a wooden spoon, and add in cocoa, flour, salt and baking powder. Stir mixture lightly until well combined.
Using a scoop, fill your cupcake liners 3/4 way (almost to the top).
Bake for 30 minutes, allow to cool in plan for 5 minutes and then remove to a cooling rack.