Cook the onion, garlic, celery, basil, and parsley in the olive oil in a large saucepan for 15 minutes over medium-low heat, or until all vegetables are soft, and the onion is see-through. Make sure the vegetables don’t stick to the bottom of the saucepan.
Next fold in the diced tomatoes and season with however much salt you crave. Bring to a calm boil over medium heat. Place a lid on the saucepan and simmer until a thick sauce is formed, about 30 minutes.
Enjoy with any pasta type, or with any recipe needing tomatoe sauce :).