Heat wine vinegar with ½ quart water to boiling point. Pour oven meat in tall bowl. Add all ingredients. Cover and marinated overnight in refrigerator. Turn twice.
Next day, dry meat with paper towels. In Dutch oven, heat 3 tablespoons oil. Add meat.
Brown on all sides, add sliced onions from marinade. Saute with meat. Add some of the marinade with all the ingredients and ½ cup water. Simmer until meat is soft.
Remove meat, strain gravy. Thicken with flour and 4 tablespoons sour cream. Serve with potato dumplings.