1 Preheat oven to 350°F. Grease and flour 13x9-inch baking pan. Mix flour, baking powder and salt in medium bowl. Set aside. Microwave butter and milk in medium microwavable bowl on HIGH 2 minutes or until butter is melted. Stir in vanilla. Set aside.
2 Beat eggs in large bowl with electric mixer on medium speed 5 minutes or until fluffy. Gradually add sugar; beat well. Alternately add dry ingredients and milk mixture, beating on low speed after each addition just until mixed. Pour into prepared pan.
3 Bake 35 to 40 minutes or until toothpick inserted into center comes out clean. Cool in pan on wire rack. Sprinkle with confectioners' sugar, if desired.