In a medium pot, place the tomatoes, onion, garlic and butter and bring the sauce to a boil.
Then add in the basil and simmer the sauce on a lower heat for about 40 minutes.
Next, take out the onions and garlic and season the sauce with some salt and pepper. Then transfer the sauce to a food processor and pulse until smooth and check it again to see if it needs more salt or pepper.
I serve this with angle hair pasta and some parmesan cheese and it is the easiest and best tomato sauce ever! I also top this with some more fish basil and enjoy! :)