My go-to marinara sauce

This is from my friend Heidi...it's a keeper! It's super easy if you have a food processor to chop the carrots, onions and celery.

1/8 cup extra-virgin olive oil
1 small onion, finely chopped
1 garlic clove, finely chopped
1 celery stalk, finely chopped
1 carrots, peeled and finely chopped
1/2 teaspoon salt
1/2 teaspoon freshly ground black pepper
1 (32-ounce) cans crushed tomatoes (I like the Italian ones)
1/2 cup of grated Parmesan-Regiano cheese

Directions
In a large pot, heat the oil over a medium-high flame. Add the onions and garlic and saute until the onions are translucent, about 10 minutes. Add the celery, carrots, and 1/2 teaspoon each of salt and pepper. Saute until all the vegetables are soft, about 10 minutes. Add the tomatoes and simmer uncovered over low heat until the sauce thickens, about 1 hour. Stir in the Parmesan cheese and season the sauce with more salt and pepper, to taste.