Green Tomato Jam - Marmellata Di Pomodori Verdi Recipe

Directions:

1. Core the tomatoes, halve them, and dig out the seeds with a table knife. Cut the tomatoes into 3/4 cubes (or smaller if you like).
2. Put a small plate in the freezer. You will use it later to test for doneness.
3. Place the tomatoes in a heavy 6-quart pot with the sugar, lemon zest, and lemon juice. Stir well, then bring to a boil over moderate heat. Reduce the heat to maintain a slow simmer and continue cooking until the tomatoes become translucent and the syrupy liquid thickens considerably, about 40 minutes, stirring occasionally to prevent the jam from sicking. (Note: towards the end keep an eye on it so it doesn't burn). When the jam reaches 215 degrees F (102 degrees C) on a candy thermometer, remove the chilled plate from the freezer and spoon a little jam onto it.
4. Return the plate to the freezer until the jam is cold. Test it for doneness (my note: prod it with your finger, if it seems to be developing a surface skin and solidifying it is ready), and if the jam is still too runny, continue cooking it. Otherwise remove pot from heat.
5. This will produce 2 pints or 4 half-pints worth of jam that can be processed via Water-Bath Canner. Fill jars to 1/2 below the rim to allow for appropriate headspace. Process the jars in the canner for 15 minutes.