You can use varying amounts of these ingredients with good success.  Start with marrow bones with a little meat on them.  Drizzle over bones tomato paste.  Bake for several hours.  Transfer bones to a large kettle.  Pour fat off pan where bones were cooked and add water to de-glaze.  Pour over bones along with several carrots, several stalks of celery and two or three onions.  Add water to barely cover and simmer until vegetables are well done.  Strain.  Discard vegetables and bones and add salt and pepper to taste to the broth.  Use for vegetable soup, gravy, or meat sauce.