Frosting: Preheat the oven to 350 degrees F (175 degrees C). Grease and flour an 8-inch square pan. Melt 1/2 cup butter in a large saucepan. Remove from heat, and stir in sugar, eggs, and 1 teaspoon vanilla. Beat in 1/3 cup cocoa, flour, salt, and baking powder. Spread batter into prepared pan. Bake in…