Melt
the butter in a small pan, then mix in the biscuit
crumbs. Press the mixture over the base of the cake tin,
then chill in the refrigerator for about 15 minutes
until firm.
Beat
the ricotta cheese with the egg yolks, almonds and lemon
rind until smooth, then gradually stir in the cream.
Whisk the egg whites until stiff, then whisk in the
sugar a little at a time. Carefully fold into the cheese
mixture, then spoon over the biscuit base and level the
surface.
Bake in a preheated oven, 160°C (325°F), Gas
Mark 3, for 1-1 1/4 hours until firm. Turn off the heat
and leave the cheesecake in the oven until cold.
Put in
the refrigerator and chill. To serve, dust with a sifted
icing sugar and sprinkle with lemon rind.