Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
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. Combine the flour, baking powder, and salt; stir into the creamed mixture alternately with the milk.
Spread half of the batter into the prepared pan. Arrange half of the sliced strawberries over batter. Spread remaining batter over strawberries; top with remaining strawberries. Bake for 40 to 45 minutes in preheated oven.