Wash and dice vegetables such as onion, carrot, celery, and potato.
Heat olive oil in a pot and sauté the onion until fragrant.
Add the remaining vegetables and stir-fry together.
Add tomatoes (canned or fresh) and mix well.
Pour in vegetable broth or water and bring to a boil.
Season with salt and pepper to taste.
Simmer over medium-low heat until all vegetables are cooked through.