Slow Cooked Summer Tomato Sauce - Lidia

Ingredients

• 8 pounds ripe plum tomatoes
• 3/4 cup extra-virgin olive oil
• 5 cups finely chopped onions, about 1 1/4 pounds
• 1/3 cup finely chopped garlic
• 2 teaspoons salt, plus more to taste
• 1/2 to 1 teaspoon peperoncino (to your taste)
• 8 large branches of basil with lots of leaves (or smaller stems, tied together)
• water