Cut the cabbage, onion, carrot, celery, and bell pepper into bite-sized pieces.
Heat olive oil in a pot and sauté the onions.
Add the rest of the vegetables and stir-fry for another 2-3 minutes.
Add tomatoes (canned or fresh) and pour in water.
Season with salt and pepper, then bring to a boil.
Boil on high heat, then reduce to medium-low and simmer for 20 minutes until the vegetables are cooked through.