Preheat oven to 160 °C convection oven. Peel and finely dice onions, garlic cloves and carrots. Wash celery and dice finely as well. Season pork knuckle slices with salt and pepper and flour a little.
Heat olive oil in a saucepan and brown meat on both sides. Set meat aside.
Add vegetable cubes to pot and sauté in drippings until hot. Deglaze with white wine and chicken soup. Add bay leaves, lemon and orange zest to pot and bring everything to a boil. Add meat back in and cover and cook in oven for 1 1/2 hours.
In a pot, bring water to a boil, cut tomatoes and blanch in it. Peel and cut tomatoes in half. Remove seeds and finely dice flesh.
Add tomatoes to the stew. Season ossobuco with red wine vinegar, salt and pepper and simmer together with the tomatoes for another two minutes over medium heat.
Decorate ossobuco with celery greens or thyme sprigs and serve.