Heat 1⁄2 cup of the oil and 8 tbsp. of the butter in a large pot
over medium heat. Add onions and cook, stirring often, for about 2 minutes. Add carrots, celery, peppers, leeks, and fennel and cook, stirring often, for about 5 minutes. Add crushed tomatoes, tomato paste
, 4 cups water, bay leaves, oregano
, thyme, basil, and cayenne and season to taste with salt and pepper. Bring to a boil, reduce heat to low, and simmer, stirring occasionally, for 2 hours.