In a big bowl mix the onion, apple, breadcrumbs, garlic, cinnamon, olive oil, pepper and salt.
Preheat the oven to 220 degrees C.
Lay out the boned leg of pork, you may need to make some extra cuts to get it as flat and even as possible.
Lay the stuffing mixture evenly over the leg of pork. Roll the meat firmly. Tie the string around the meat at 3cm intervals. Rub the outside of the rolled meat with the oil and salt.
Place the rolled meat in a roasting tray. Cook for 30 minutes at 220 degrees C then reduce the temperature to 160 degrees C and cook for a further 90 minutes or until the meat is cooked to your liking.