In a soup pot, soak the black beans in the 6 cups of water overnight.
Drain the soaking water and return the beans to the soup pot. Add 7 cups of vegetable broth, tomatoes, celery, carrot, onion, garlic, bay leaves, oregano, basil and marjoram. Cook for 2 to 2 1/2 hours until beans are soft.
Add the lemon juice and sherry. For a sharper taste add 1/4 cup apple cider vinegar. Remove the bay leaves and blend soup in food processor or blender. Add salt and pepper to taste.
Return to soup pot and reheat. Serve garnishing each bowl with chopped green onions.