- Preheat oven to 350 degrees F (175 degrees C).
- Cut out 4 12x12 inch sheets of aluminum foil. Place one sliced potato, one sliced onion, 1 tablespoon butter and one slice of cheese on each aluminum foil square. Wrap the foil around the sides of the potatoes and onion to form a cup. Pour 1/4 cup of water into each pouch and fold the top of aluminum foil over the potatoes to close it.
- Bake in a preheated 350 degrees F (175 degrees C) oven for 60 minutes.