Prepare the roast: Preheat oven to 175 degrees. Rinse meat cold, dab dry and season well with salt and pepper. Cut onions and garlic into slices. Heat 2 tablespoons of oil in a roasting pan, fry meat all around, add onions and garlic and fry both briefly.
Add the tomatoes and braise in the oven for 80 minutes.
Cut vegetables: Wash, clean, quarter and cut the rest of the vegetables. After 80 minutes add the thyme to the meat and let it stew for another 30 minutes.
Prepare side dishes: Prepare polenta according to package instructions. Spread 2cm high on a greased baking tray, let it cool down and then cut it into pieces. Just before serving, heat the remaining oil in a pan and fry the polenta slices until golden brown.
Cut the meat open: Wrap the roast in aluminium foil and let it rest for 10 minutes. In the meantime season the vegetables with balsamic vinegar, salt, pepper and 1 pinch of sugar. Cut the meat into slices and serve with polenta and vegetables.