Method:
Mix together cheese, sugar, salt and lemon zest in a large bowl; set aside. Mix together lemon juice, lemon liqueur and 2 teaspoons cold water in a medium bowl; set aside. Working with one at a time, soak cookies in lemon liqueur mixture briefly, then arrange in the bottom of a large glass serving bowl. After covering the bottom, place the soaked cookies up the sides of the bowl, overlapping slightly if necessary to cover the bottom and sides of the bowl completely. Add all ricotta mixture to bowl and press down slightly with a spatula. Cover the top with the remaining soaked cookies, then cover bowl with plastic wrap and refrigerate for 2 hours. Unmold tiramisu onto a large serving plate, or scoop directly from the bowl. Serve cold.