Heat olive oil in a large stock pot over medium-high heat. Add the onions and saute until soft, about 8 to 10 minutes.
Add garlic and saute for 1 minute. Add celery and carrots and saute until the vegetables are soft, about 10 minutes.
Add the crushed tomatoes, bay leaves, oregano, basil, salt, and pepper. Bring to a simmer and reduce heat if needed. Continue to simmer (uncovered) for 45 minutes to 1 hour, until the sauce is thickened.
Remove bay leaves and discard. Season the sauce with salt and pepper to taste.
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NOTES: If your sauce is too acidity you can add small amounts of sugar (or a sugar substitute) to counteract that. Adjust any seasoning to taste.
VARIATIONS: Brown ground beef or Italian sausage and add to sauce. Meatballs can also be added.