Cut cabbage, onion, carrot, celery, and bell pepper into bite-sized pieces.
Heat olive oil in a pot and sauté the onions.
Add carrot, celery, bell pepper, and cabbage in order, and stir-fry.
Add tomatoes and water, then bring to a boil.
Season with bay leaf, salt, and pepper.
Simmer over medium heat until the ingredients are tender.
Serve the finished soup in a bowl.