Clean and cut vegetables like onion, carrot, and celery into bite-sized pieces.
Heat olive oil in a pot and sauté the onions until fragrant.
Add carrots, celery, and garlic, and sauté together.
Add tomatoes (canned or fresh) and mix well.
Pour vegetable stock and bring to a boil.
Season with bay leaf, salt, and pepper.
Simmer over medium-low heat until the vegetables are soft.
Serve the finished soup in bowls.