Preheat oven to 350 degrees F (175 degrees C). Grease an 8 inch square pan.
In a large bowl, blend melted butter, sugar and vanilla. Beat in eggs one at a time. Combine the flour, cocoa, baking powder and salt. Gradually blend into the egg mixture. Spread the batter into the prepared pan.
Bake in preheated oven for 40 to 45 minutes, or until brownies begin to pull away from the sides of the pan. Let brownies cool, then cut into squares. Enjoy!