Heat oil in large saucepan over medium.
Add onion and saute until soft.
Add garlic, salt and pepper. Saute 2 minutes more.
Add tomatoes (with juice) and increase heat to med-high.
If using whole plum tomatoes, break them up slightly in the pan with a wooden spoon.
Once boiling, reduce heat to low and simmer 20-30 minutes, until thickened.
Stir in the basil last and serve over any pasta!
Top with parmesan cheese (optional).