Finely chop onion, carrot, celery, and bell pepper.
Heat olive oil in a large pot and sauté the onion.
Add carrot, celery, and bell pepper, and sauté lightly.
Pour in diced tomatoes and water.
Add cabbage and bring to a boil.
Season with bay leaf, salt, and pepper.
Simmer over medium heat until all the vegetables are tender.