Preheat oven to 350F. Grease and flour an 8-inch square pan.
In a large saucepan, melt butter, remove from heat, and stir in sugar, eggs, and vanilla. Beat in cocoa, flour, salt, and baking powder. Spread batter into prepared pan. Bake 25-30 minutes.
Variation: Add 1 Tsp mint extract for mint brownies.