Preheat large dutch oven or heavy bottom pot on low-medium heat and add olive oil. Add onion and garlic, cook for 8-10 minutes or until translucsent, stirring occasionally.
Add crushed tomatoes, sugar, oregano, salt, pepper and stir. Cover with a lid and bring to a boil, then reduce to low heat and simmer marinara sauce for 30 minutes. Stir a few times to avoid scorching.
Turn off heat, add fresh basil, stir, cover and let marinara sauce rest for 30 minutes to allow flavors develop.
Taste and adjust any seasonings, if you wish. Serve alongside meatballs, as a dip and use in your favorite dishes.
Notes
Store: Refrigerate in an airtight container for up to 1 week.
Freeze: Fully cook, cool completely and freeze in an airtight container for up to 3 months. Thaw overnight in the fridge.