In a large mixing bowl beat eggs at high speed until thick, about 5 mins. Gradually add sugar beating until the mixture is light and fluffy. Combine flour and powder; add to batter with vanilla and beat at low speed until smooth.
Meantime, heat the milk and butter until the butter melts. Stir occasionally. Add the hot milk and butter to the batter beating until combined. Pour into a greased & floured 13x9 pan. Bake at 350 degrees for 30-35 minutes.