In a separate bowl, combine flour, cocoa, baking powder, and salt.
Gradually blend the flour mixture into egg mixture until thoroughly blended. Stir in nuts at this point if desired.
Spread the batter into a greased, 8-inch square baking pan.
Bake at 350F for 30-35 minutes, or until the brownie begins to pull away from edges of the pan.
Cool in pan, frost if desired.
Cut into squares to serve.