Crostata

Work the soft butter with the sugar, egg and lemon zest. Add gradually the flour, form a ball and let it sit in the refrigerator at least 3 hours. Preheat the oven to 180°C (Thermostat 6). Roll out the dough, not too thin, and garnish the tart moulds or cut around them with a pastry cutter. Fill each tart with jam and bake 15 to 20 minutes. Allow to cool before serving: jam will congeal while cooling.