Cut onion, cabbage, carrot, tomato, celery, and bell pepper into bite-sized pieces.
Heat olive oil in a pot and sauté the onion.
Add cabbage, carrot, celery, and bell pepper, and stir-fry together.
Add tomatoes, stir, and pour in water.
Season with pepper and salt.
Once it starts to boil, reduce to medium heat and simmer until the vegetables are cooked.