This definitive recipe has been my go-to for years. Although the directions say to discard the onion before tossing the sauce with pasta, I leave the onion in and find that white or red varieties work equally well. This recipe makes four servings or enough sauce for a pound of pasta.
2 cups tomatoes, in addition to their juices
5 Tbsp. unsalted butter
1 small white or red onion, peeled and cut in half
Kosher salt to taste
Shaved Parmesan cheese (optional garnish)
Fresh basil leaves, ripped (optional garnish)
Combine the tomatoes, their juices, the butter and the onion halves in a saucepan. Add a pinch or two of salt.
Place over medium heat and bring to a simmer. Cook, uncovered, for about 45 minutes. Stir occasionally, mashing any large pieces of tomato with a spoon. Add salt as needed.
Remove and discard the onion. Serve over hot pasta and top with shaved Parmesan and fresh basil, if desired.