Cream sugar and butter together; add eggs and mix. Blend flour, salt and baking powder together and add to mixture. Mix soda with milk and vanilla; mix all together. Add apple slices and pour batter into a buttered baking dish. In a separate bowl, combine brown sugar, flour, cinnamon and butter, mixing until crumb texture; sprinkle over apple batter. Bake at 375ºF. for 35 to 40 minutes. Serve hot with rich milk, Half and Half or a scoop of ice cream. Makes 4 generous servings.