Ricotta-Filled Cake from Sicily

This is the most lavish and wonderful of all Sicilian desserts—a rum-sprinkled pan di Spagna sponge cake with a creamy ricotta filling, just like the type used to fill cannoli. The outside is covered with a sheet of pale green almond paste, giving the cake a tailored, delicious finish. In Sicily, a sugar icing is often poured over the almond paste covering. I have omitted this final step, since most Americans would find it excessively sweet. Though cassata