Heat oil in a large skillet on medium-low.
Cook onion, 10 12 mins stirring occasionally.
Add red pepper for one minute.
Increase heat to medium and add tomatoes.
Season with salt. Add bayleaf.
Cook 20-25 mins. stirring occasionally.
Remove from heat and add basil. (Remove bay leaf)
Coat pasta with butter and parmesan, then add to sauce.