Wash the green tomatoes and remove their pedicles. If necessary, remove some of the seeds, if there are rough parts and cut them into small pieces. Put them to boil in different water 3 separate times. This is done in order to drain the bitterness out of the green tomatoes.
The third time, their skins can be easily peeled. Prepare a sugar syrup using 2 cups of water, sugar and add the lemon leaves. Once the syrup is slightly thickened, add the tomatoes and mix them. Boil the jam until slightly thickened, add the walnuts and boil to the desired consistency.
2 minutes before removing from the heat, mix in the citric acid. Remove the green tomato jam and distribute it in dry and warm jars. Remove the lemon leaves.
Close the jars and sterilize them for 10-odd minutes.