Then, pre-heat oven to 375 degrees F. While the oven is heating, make a batter for the cake mixing all the ingredients in the following order: combine flour, baking powder and salt in a small mixing bowl and set it aside. Beat butter or margarine with a hand mixer at medium speed for 30 seconds in a large mixing bowl. Add sugar and vanilla and beat well. Add eggs, one at a time, beating well after each addition. Add dry flour mixture and milk alternately, beating on low speed after each addition until just combined.