In a large bowl crush the San Marzano tomatoes with your hands.
In a large pot heat olive oil over medium heat. Sauté onions until translucent.
Add garlic and Calabrian chili pepper paste to the pan. Sauté for 30 seconds until fragrant.
Transfer tomatoes to the pot and bring to a simmer. Add the bay leaf and butter. Partially cover with a lid, simmer over low heat for approximately an hour, and stir often.
Remove from heat and stir in town basil leaves. Season with salt to taste.
Serve with your favorite pasta or in place of a traditional marinara sauce.