Preheat oven to 180 degrees C and grease a medium sized casserole dish.
Line bottom and sides of dish with the sliced potatoes. Lay half the sausages (cut the thin sausages in half lengthways) on top, then another layer of onion rings, then cover with half tin tomatoes. Season with pepper.
Place another layer of potato slices, sausages and onion rings over this then add the remaining tomatoes and season once again with pepper. Cover with a thin layer of potato slices, dot with butter and place in oven.
Cook for 45mins to an hour until the potato topping is well browned. Serve topped with grated cheese.