Peel, seed and dice tomatoes into 1/2-inch pieces. Place in heavy enamel or stainless steel pan. (Aluminum pans will react with the acidity in this dish.)

Bring to a boil, then reduce heat to medium low heat. This will need to cook for about 1-1/2 to 2 hours.

Stir occasionally at first, then check more frequently at end of cooking time to prevent scorching on bottom of pan. When jam is thick and shiny, and volume is about 4 cups, it is done. Let cool in shallow pan. Keep refrigerated. Let come to room temperature, or warm slightly to serve.

Recipe and Photo Courtesy The California Tomato Commission.