Heat oven 350°F. Grease 13x9x2 in baking pan

Place butter in bowl microwave until melted. Stir in sugar and vanilla. Add eggs one at a time beating well with spoon after each. Add cocoa; beat until well blended. Add flour baking powder and salt beat well. Stir in nuts if wanted. Pour batter into prepared pan.

Bake 30 to 35 minutes or until brownies begin to pull away from sides of pan. Cool completely in pan on wire rack. Cut into bars