PREHEAT oven to 350º F. Grease 13 x 9-inch baking pan.
COMBINE granulated sugar, butter and water in large bowl. Stir in eggs and vanilla extract. Combine flour, cocoa, baking powder and salt in medium bowl; stir into sugar mixture. Stir in nuts. Spread into prepared baking pan.
BAKE for 18 to 25 minutes or until wooden pick inserted in center comes out slightly sticky. Cool completely in pan on wire rack. Sprinkle with powdered sugar. Cut into bars.