Core the tomatoes and chop finely (no need to peel and remove seeds). Combine all ingredients in a large stainless steel or other non-reactive pot. Bring mixture to a boil over high heat; once boiling, reduce heat to low.
Simmer jam for 1-1/2 to 2 hours, stirring the mixture regularly until it is thick with jammy goodness and a sample falls off a spoon with a slow plop. Use a canning funnel to transfer jam to hot, sterile 4 – 8 oz jars.
This recipe makes about 2-3 pints. A covered jar of jam will keep in the refrigerator for up to 6 months. For longer storage, leave about 1/2″ of “head space” as you fill the jars with the jam, seal with a sterile lid, and process in a boiling water bath as you would for other jams and jellies.