Drawing from trusted French regional cuisines, this green tomato jam transforms unripe tomatoes into a tangy, settable preserve. Wash the tomatoes, pat dry, remove stems, and cut into quarters. Layer in a large preserving pan with the sugar and mix well.
Grate the zest from the grapefruit and squeeze its juice. Stir into the pan. Bring to a boil over medium heat, then reduce to a gentle simmer for 30 minutes, until the mixture thickens.
Meanwhile, peel and core the apples, then cut into thin strips for natural pectin to ensure a good set. Add to the pan and simmer for another 30 minutes.
Test the set: Place a teaspoon of jam on a chilled saucer in the freezer for 3 minutes. Push with your fingertip—it should wrinkle. If too runny, cook a bit longer.
Once ready, ladle into sterilized, warm jars. For a secure seal, invert jars until cool (a traditional French method). Label and store in a cool, dark, dry place.
Customize your batch: For 1.5 kg tomatoes, add 100g chopped candied ginger; or for 1 kg, try 200g raisins or finely sliced lemon zest.
Source: Regional Cuisines of France
