A few tomatoes are broiled, skinned and mixed with a small amount of chopped ham, onion and some salt, oil, basil and other spices. This mixture is boiled and passed through a sieve and a clove of garlic is added, but removed before the sauce is passed through the sieve.
Source: ''The Cook's Decameron: A Study In Taste, Containing Over Two Hundred Recipes For Italian Dishes'' from a project that puts out-of-copyright texts into the public domain. This is from a very old source, and reflects the cooking at the turn of the last century. Update as necessary.