Heat the oil in a heavy soup pot over medium-high heat and add the beef. Sear the meat on all sides, remove it from the pot and set aside. In the same soup pot, add the carrots, celery, onion, garlic and cabbage; saute the vegetables 5 minutes. Add the seared beef back to the pot along with the beets, beef broth, sugar, vinegar, salt and pepper. Bring the soup to a boil; skim any scum that may rise to the surface then lower the heat to a slow simmer. Cook the soup slowly for 2-3 hours. Stir in the dill; cook the soup an additional 10 minutes. Serve the soup in warm soup plates, and, if desired, stir a dollop of sour cream into each cup.