Combine all ingredients in a low, wide, non-reactive pot (stainless steel is best, because if you experience any scorching or burning, you can scrub it easily). Bring to a boil over high heat and then reduce temperature to medium high.
Stirring regularly, cook the jam at a low boil until it reduces to a sticky, jammy mess. This takes anywhere from 1 to 2 hours, depending on the heat of your stove, the width of your pan, and the water content of your tomatoes.
Towards the end of cooking, as the jam begins to thicken, reduce the heat to medium and continue to stir. This jam has a tendency to burn at the very end of cooking time, as the sugars concentrate and the temperature level in the pan increase.
When you're 15 or 20 minutes out from the jam being finished, prepare a boiling water bath canner and 6 or 7 half pint jars (the yield will be between 5 and 7 half pints). Place lids in a small pan of water and bring to a bare simmer.
Once the jam is thick and there is no visible water separating out from the fruit, it is done. Remove the pan from the heat and stir for 2 to 3 minutes. This helps evaporate out the last of the water and will give you a better set when the jam cools.
Funnel jam into prepared jars, leaving 1/2 inch headspace. Wipe rims, apply lids and rings, and process in a boiling water bath canner for 15 minutes.
When time is up, remove jars and place them on a folded kitchen towel to cool. When jars are fully cool, remove rings and test seals. Sealed jars are shelf stable. Any unsealed jars should be refrigerated and used promptly.