Peel one Kg. quinces, cut into thin slices and lay in a bowl; spray with juice of two lemons and add a dash of lemon rind.
Put in a saucepan, cook for 40’, puree mixture in blender and mix in 1 Kg. sugar and ½ glass water. Place back over heat and bring to a boil, constantly skimming off foam. Simmer over moderate heat until mixture is thick enough; hermetically seal and keep upside-down for ten hours before storing.