oil to help prevent sticking.
Add the crushed tomatoes or tomato puree to the slow cooker. Stir in the kosher salt until evenly distributed.
Scatter the butter pieces over the surface of the tomatoes. Do not stir; the butter will melt and slowly enrich the sauce as it cooks.
Cover the slow cooker with the lid and cook the tomato mixture on LOW for 4 to 5 hours, or on HIGH for 2 to 2 1/2 hours, until the sauce is bubbling
