Wash the tomatoes, dry them, remove the peduncle and cut them into quarters. Put them in a jam bowl, add the sugar and mix.
Grate the zest of the grapefruit and squeeze out the juice. Add them to the basin. Bring to the heat, then, when boiling sets in, cook at a very low simmer for about 30 minutes until the preparation thickens.
Meanwhile, peel the apples and core them. Cut them into thin strips and add them to the basin (to have a sufficient proportion of pectin to ensure a smooth grip). Continue cooking for about 30 minutes.
Check the set of the jam:pour 1 teaspoon of jam into a saucer and put it in the freezer, after 3 minutes, push it with your fingertip:it should crease slightly. If it is still runny, continue cooking for a few seconds.
As soon as the jam is cooked, pour it into boiled and wiped jars. (I personally turn the jar upside down and let it cool like this). Cover, label and store in a cool, dry place away from light.
Homemade jams accept various flavors. For the green tomato jam, try 100 g chopped candied ginger (for 1.5 kg of jam), finely sliced lemon zest or raisins (200 g for 1 kg of tomatoes).
Source:Regional Cuisines of France
