Tie the leg slices around with kitchen twine. Season with salt and pepper and turn in the flour. Knock off excess flour. Sear the leg slices in hot olive oil. Take out and then sauté the onions with the garlic in the frying fat. Deglaze everything with Marsala. Add the tomato pieces and bring to the boil. Then add the leg slices again and simmer everything over a very low heat for about 2.5 hours. It should just bubble away like that. Turn meat slices more often.
The meat is soft when it begins to peel off the bone.
Season the sauce with salt, pepper and a pinch of sugar.