Preheat oven to 350°. In a large bowl, beat eggs on high speed for 5 minutes or until thick and lemon-colored. Gradually add sugar, beating until mixture is light and fluffy. Beat in vanilla. Combine flour and baking powder; gradually add to batter beating on low speed until smooth. , In a small saucepan, heat milk and butter just until butter is melted. Gradually add to batter; beat just until combined. , Pour into a greased 13x9-in. baking pan. Bake until a toothpick inserted in the center comes out clean, 30-35 minutes. Cool on a wire rack.