Green tomatoes and Walnuts Jam

2 kg green tomatoes, 2 kg sugar, 250 ml vinegar, 250 g walnuts, 2 slices of lemon

Wash and cut the tomatoes in quarters or smaller. Put them in a pan, cover with water (3 cm over them), add the vinegar and let them boil for 25 minutes. Drain well. Meanwhile make a syrup from 2 kg of sugar and 1/2 l water. Boil the syrup for 20 minutes and then add the tomatoes. After 15 minutes add the walnuts and the lemon slices. Boil for another half an hour and then put them in sterilised jars.