In a large mixing bowl, blend together sugar, butter and egg. Beat until thoroughly blended. Sift flour, baking powder and salt together. Stir milk into sugar-butter-egg mixture. Add dry ingredients to milk mixture and stir until thoroughly blended.
Spread batter into an 8 inch square, heat resistant, non-metallic baking dish. Arrange apple slices in a design on top, pressing them slightly into the batter. Combine cinnamon and sugar in a small bowl and sprinkle on top of apple slices. Heat, covered with clear plastic wrap, 5 minutes in Microwave Oven. Uncover and heat an additional 4 minutes or until apples are tender and a toothpick inserted in center comes out clean. Allow to stand 10 minutes before serving.