Preheat oven to 350 degrees F (175 degrees C). Grease and flour one 8x8 inch pan.
In a medium bowl, mix together the flour, baking powder and salt.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Beat in the dry ingredients alternately with the milk.
Pour batter into prepared pan. Bake for 25 to 30 minutes in preheated oven. Cake is done when it springs back to the touch.