Preheat oven to 350. Spray 8" square baking pan with cooking spray. In small bowl combine flour, cocoa and baking powder. In medium bowl stir together sugar, brown sugar, oil and prune puree. Add egg whites and vanilla. Gradually stir in cocoa mixture until blended. Pour into prepared pan and bake 15 to 20 minutes or until brownies begin to pull away from sides of pan. Sprinkle with confectioner's sugar. 12 Servings. Calories: 121;Fat: 3 grams.