Cut the onion, carrot, cabbage, celery, and tomato into bite-sized pieces.
Add olive oil to a pot and sauté the onions.
Add carrot, celery, and cabbage and stir-fry together for 3 minutes.
Add chopped tomatoes and water, then bring to a boil.
Add bay leaf, salt, and pepper, and simmer on medium-low heat for 20 minutes.
Add zucchini at the end and simmer for an additional 5 minutes.
Finish with lemon juice or parsley to taste.