Trim the meat and rub with salt.
Wash the leek and cut into rings. Peel and chop the carrots and celery. Peel and chop the garlic.
Heat the oil in a large frying pan and sauté the meat until browned all over.
Remove the meat from the pan and season with pepper. Add the vegetables to the pan and sauté for 5 minutes. Season with salt, pepper and lemon zest. Add the tomato paste and saute for 1-2 minutes.
Pour in the wine and stock, add the meat and cook, covered, for 21/2 hours, turning occasionally.
Remove the meat from the sauce and pour the sauce through a sieve.
Wrap the meat in foil and let it rest.
Season the sauce. Mix the cornflour with the cream and stir into the sauce to thicken. Slice the meat and serve with the sauce. Serve with dumplings if desired.