Stir together cornmeal, flour, baking powder, and salt in a mixing bowl. In another bowl lightly beat together buttermilk, eggs, and melted margarine or butter. Add to flour mixture and stir just until batter is smooth (do not overbeat). Pour into greased 9x9x2-inch baking pan. Bake in a 425 degree F oven for 25 to 30 minutes or until golden brown. Serve warm. Makes 8 or 9 servings.