Melt butter in an 8-inch square cake pan. Add brown sugar; blend with the butter. Arrange 5 or 6 pineapple slices over the bottom of the pan, cutting as needed to fit as many as possible.
In a mixing bowl, cream shortening, vanilla, and granulated sugar. Add egg; beat thoroughly. Add sifted dry ingredients alternately with the milk. Pour batter over pineapple. Bake at 350° for 35 minutes, or until a wooden pick or cake tester inserted in center comes out clean.
Calories per serving, based on 9 servings: 268