Clean and dice onion, carrot, celery, and cabbage.
Put olive oil in a pot and sauté the onion.
Add carrot, celery, and cabbage and stir-fry together.
Add diced tomato and water, then bring to a boil.
Season with bay leaf, salt, and pepper.
Simmer over medium-low heat for about 20 minutes.
Remove the bay leaf and it's ready to serve.