Cakes made with ricotta cheese, such as this one, are very typical of Italian desserts. Here, bread crumbs serve as the crust.
Spoon the ricotta into a large fine-mesh sieve or a colander lined with a double thickness of cheesecloth or basket-type coffee filter. Set the sieve over a bowl and cover the ricotta well with plastic wrap. Drain in the refrigerator at least overnight, or up to 24 hours. Discard the liquid in the bottom of the bowl.
In a small bowl, soak the raisins in rum, tossing occasionally, until the raisins are softened and have absorbed most of the rum, 1 to 2 hours.
Smear an 8-inch springform pan with enough softened butter to coat lightly. Sprinkle the bread crumbs over the butter to coat generously. Shake out the excess crumbs. Preheat oven to 375°F.
In a large bowl, use a whisk to beat the egg yolks, sugar, and salt until pale yellow, Add the drained ricotta and lemon and orange zest, and beat until blended thoroughly. Beat in the heavy cream. Use a rubber spatula to fold in the pine nuts and the raisins and rum. In a separate bowl, beat the egg whites with a handheld electric mixer or wire whisk until they form stiff peaks. Fold about one-fourth of the egg white into the ricotta mixture to lighten it--use a large rubber spatula to scrape the batter from the bottom of the bowl up and over the whites. Fold in the remaining egg whites in the same way.
Pour the ricotta mixture into the prepared pan, and bake until the cake is golden brown on top and set in the center, about 1 hour and 10 minutes.
Cool the cake completely before removing the sides of the pan. Serve the cake at room temperature or chilled.