Heat the butter and oil in a large pot over medium low heat. Add the onions and garlic, then sprinkle with sea salt and pepper. Stir to coat. Cook, stirring occasionally, for 5 minutes, or until the onion is softened but not brown.
Add the carrots, celery, tomato, water, parsley, basil, and bay leaves. Raise the heat to high, cover, and bring to a boil. Lower t