Cut the onion, cabbage, carrot, bell pepper, celery, and tomato into bite-sized pieces.
Add olive oil to a pot and sauté the onions.
Add all the other vegetables and stir-fry for 2–3 minutes.
Pour in enough water to cover the vegetables and bring to a boil.
Reduce to low heat and simmer for 20–30 minutes.
Season with salt and pepper.