Grate the limone rind and then squeeze the juice of the three limone into the bowl.
Place the limone juice, zucchero and limone rinds in a saucepan and bring the mixture to a boil.
Turn the heat to low for about 5 minutes until a thick, syrupy liquid forms.
Cool the mixture to room temperature and mix in the 2 cups of cold water.
Pour the mixture into a shallow container and then cover it with a lid or cling wrap.
Freeze the granita for about an hour and then use a fork to break it up. Put it back into the freezer and repeat three times, every hour, for 3 hours.
Scoop the granita out of the container and enjoy!