1Heat oven to 350°F. Spray 8- or 9-inch square pan with cooking spray.
2In medium bowl, mix granulated sugar, yogurt, oil, vanilla and egg whites. Stir in all remaining ingredients except powdered sugar. Spread in pan.
3Bake 25 to 30 minutes or until toothpick inserted in center comes out clean. Cool completely, about 1 hour. Cut into 4 rows by 4 rows. Sprinkle with powdered sugar just before serving.