Heat oil and add onions, celery, and seasoning:
Heat oil in a large stockpot over medium heat. Add onions or leeks, celery, and Italian seasoning; season with salt and pepper.
Sauté:
Cook, stirring frequently, until onions are translucent, 5 to 8 minutes.
Add tomatoes and liquid and simmer:
Add broth, tomatoes and their juice, tomato paste, and 3 cups water to pot; bring mixture to a boil. Reduce heat to a simmer, and cook, uncovered, 20 minutes.
Stir in vegetables and finish soup:
Add vegetables to pot, and return to a simmer. Cook, uncovered, until vegetables are tender, 20 to 25 minutes.
Season and serve:
Season with salt and pepper, as desired. Serve or let cool completely before storing.
Storage Instructions
To store, let the soup cool completely at room temperature, then ladle it into airtight containers. Keep it in the refrigerator for up to three days or in the freezer for up to three months.
To reheat, simmer the soup in a saucepan over medium heat until warm, 10-15 minutes.
Freeze soup in small containers so you can thaw only what you need. Defrost the soup in the refrigerator overnight before rewarming.
Frequently Asked Questions
What are the best vegetables to put in soup?
Any vegetables, fresh or frozen, will work perfectly in this vegetable soup. We love some crisp options like carrots and corn, green ones like broccoli, peas, and green beans, and starchy chunks from either white or sweet potatoes.
How do you add richness to vegetable soup?
This vegetable soup is pretty light, but if you want to add heft and richness to the soup, consider adding a medley of earthy mushrooms to the onions and celery. Miso paste will also add a subtle umami flavor to soup and can be added in with the tomato paste.
Can I use fresh tomatoes instead of canned?
Yes. When tomatoes are fresh and in season, they are delicious in soup. Canned tomatoes have more liquid than fresh, so add another 1/2 to 1 cup of broth to the soup.