Note: Make this a day ahead so you can skim off the fat.
Preheat oven to 375.
Cover both sides of brisket with lots of pepper.
Over a medium flame, heat the oil in a heavy casserole or roasting dish and brown the brisket on all sides. Take the brisket out of the pan and set aside.
Add the onions to the casserole and cook them over medium-high heat. As you stir them, scrape up the brown bits from the bottom of the casserole. Cook the onions for about 15 minutes, or until they are thoroughly browned. Add the carrots, garlic and bay leaves; stir for another 1-2 minutes. Take the casserole off the burner and carefully put the brisket back into its nest of vegetables.
Coat the brisket on both sides with tomato paste. Sprinkle more pepper, and a little salt, over the tomato paste. Pour the tomatoes and red wine into the bottom of the casserole. Cover the casserole tightly, first with a layer of foil and then with the lid. Let the pot roast cook on the middle rack of the oven for 3 hours. Check the liquid level in the casserole frequently; if it gets too low, add a little water or beef broth.
When the meat is tender, take it out of the oven. Keep the meat covered while you cool it to room temperature. Then put it in the refrigerator overnight. The next day, spoon off all the solidified fat you can. Discard the bay leaves.
Bring the meat back to room temperature and reheat it along with its juices and the vegetables either on top of the stove or in the oven. When it's hot, slice it on the diagonal and serve with the pan juices and vegetables spooned over. Add salt at the table, if needed.