Combine bones, water, cabbage, onions, carrots, celery, peppercorns, and bay leaf in soup kettle. Cover and simmer 45 minutes. In a saucepan mix beets with vinegar and sugar. Add water to cover. Simmer, partially covered, 15 minutes or until tender, and set aside. Add tomatoes to kettle and simmer 10 minutes. Strain stock, pressing juice from vegetables. Cool, chill, and skim off fat. Reheat to simmer. Add beets and cooking liquid and simmer 5 minutes. Season with salt and pepper, if desired. Garnish with yogurt or sour cream and dill.