Caramelize the ingredients: In a large pot, heat the oil over medium-low heat and sauté the chopped onions until caramelized. Add garlic until lightly browned, then stir in chopped tomatoes and diced zucchini. Cook for 5 to 8 minutes until softened.
Add the spices and simmer: Mix in tomato paste, thyme, oregano, basil, a chicken stock cube, and pepper. Simmer for 20 minutes.
Blend the soup: Use an immersion blender for a smooth texture for about 2 minutes; for a chunkier soup, blend for 1 minute. Remove stringy celery bits and enhance with Parmesan or Grana Padano cheese and croutons. Flavors improve after a day or two.
Notes
Vegan - Leave out the butter and replace with olive oil or grapeseed oil. Use a plant based alternative for parmesan cheese such as Nutritional yeast.Protein - Add shredded chicken, turkey or roast beef after blending the soup for a more protein rich meal.Fresh tomatoes - Swap out with canned tomatoes from a quality brand.Zucchini - No need to peel.Thicken the soup - Use an immersion blender until the soup has the right consistency.Make ahead of time - Absolutely.