Clean and chop all ingredients, leaving the garlic whole to add at the end.
Heat oil in a medium or large saucepan. Test the oil temperature by adding a small piece of onion; when it begins to bubble, add the remaining chopped onion, carrots, celery, and oregano. Let the mixture cook down over medium heat until the onions become slightly transparent.
Incorporate fresh or canned Roma tomatoes. Mix in tomato paste, followed by parsley, basil, and salt to taste. Add whole peeled garlic clove(s), stir well, and maintain on a low to medium heat setting.
Simmer the sauce until the garlic becomes soft, about thirty minutes.
Optional, use an immersion blender to gradually blend the sauce until no vegetable chunks remain. Blend to achieve your desired consistency.
Serve and enjoy.
