Fry the pork slices until they are crisp. Remove them, and cook the onion cut in thin slices in the fat. Turn the slices often to avoid burning. Season with pepper and then put a layer of peeled sliced apples on top of the onions. Dust with the sugar and put on a lid. Bake at 400°F, 200°C, gas mark 6 for fifteen minutes. Serve with fat meat or poultry, such as pork, ham, goose or duck.