Start by peeling and roughly chopping the tomatoes.
Combine the chopped tomatoes, salt, onion halves and butter in a large Dutch Oven (or heavy bottomed pot). Bring to a boil over medium high heat, until the tomatoes start releasing their juices.
Lower the heat to a steady simmer and cook, uncovered, for 45 minutes or until thickened to the desired consistency. Make sure to simmer occasionally, using your wooden spoon to mash up the large pieces of tomatoes.
Taste and adjust salt.
Remove the onion and serve with pasta, can or freeze for later, or use it in other recipes!
