Place the pot roast in a large porcelain, glass or earthenware container. Slice 1 onion. Combine the wine, 1 pint water, wine vinegar, the sliced onion, bay leaves, peppercorns, cloves and sugar. Bring to a boil and simmer 5 minutes. Cool and pour over the meat. Cover and marinate in the refrigerator for 2-3 days. Turn meat twice daily. Remove the meat from the marinade and dry. Strain the marinade and reserve. Rub the meat with flour, salt, and pepper. Heat the butter in a large heavy saucepan or Dutch oven. Brown the meat in it on all sides. Slice and add the remaining onion, sliced carrot, tomatoes, 2 cups of the strained marinade and 2 cups water. Simmer covered 2 1/2 hours or until meat is tender turning the meat once or twice. Remove the meat and keep warm while making the sauce. Thicken the gravy in the usual manner with a little flour mixed with water. If desired, add a little sour cream Check sauce for seasoning and keep warm. Slice the meat and arrange on a heated serving platter. Pour a little sauce over the meat and serve remaining sauce in a gravy boat. Serve with spaetzle. Makes 6-8 servings.