Best Basic Brownies

1 cup butter
2 cups sugar
2 tsp. vanilla
4 eggs
3/4 cup baking cocoa
1 cup flour
1/2 tsp. baking powder
1/4 tsp. salt
1 cup chopped nuts (optional)

Preheat oven to 350*. Grease and flour a 9 by 13 inch pan.
Microwave the butter in a microwave safe bowl for until melted. Stir in the sugar and vanilla. Add the eggs one at a time, beating well after each addition. Add the cocoa; beat well until well blended. Add the flour, baking powder and salt; beat well. Stir in the nuts if desired.
Pour the batter into the prepared pan. Bake for 30-35 minutes or until brownies begin to pull away from the pan sides.