(Ceuled Lemwn) Scrub the lemons to clean them. Cut the lemons in half and squeeze out the juice and strain. Grate the rind. Pour the juice into a double saucepan. Beat the eggs and add to the juice with the sugar and butter. Stir with a wooden spoon to dissolve the sugar. Continue heating and stirring until the curd thickens. Put in sterilised jars and cover.