In a large kettle, cook the meat with salt and pepper until browned.
In a small saucepan, saute onion in butter until tender; add to kettle. Add the cabbage, carrots, celery, potatoes, tomatoes, beets, parsley, water, and vinegar; bring to a boil. Reduce heat; simmer for 50-60 minutes or until vegetables are tender.
In a small bowl, combine flour and milk. Gradually stir into soup. Bring to a boil, cook and stir for 2 minutes or until thickened.