In a bowl, soak the raisins in the rum until they are nice and plump, about 40 minutes. Preheat the oven to 325°F. Generously butter an 8-inch springform pan. Add the cookie crumbs to the pan to coat it evenly, then tap out the excess.

In a large mixing bowl, beat the ricotta lightly. Gradually beat the egg yolks into the ricotta to blend thoroughly. Stir in 6 tablespoons of the sugar, the flour, lemon zest, candied orange rind, and soaked raisins and rum.

In a separate large bowl, beat the egg whites and salt until soft peaks form. Add the cream of tartar and remaining 2 tablespoons sugar and beat until stiff, glossy peaks form. Fold the egg whites into the ricotta mixture. Pour the ricotta mixture into the prepared pan, using a rubber spatula to spread the batter evenly. The batter should reach no more than halfway up the sides of the pan. Sprinkle with cinnamon.

Slide the pan onto the middle rack of the oven and bake until a toothpick inserted in the center of the cake comes out fairly clean and the top is golden, about 1 hour. Turn off the oven and leave the ricotta pudding inside with the door closed for 30 minutes. Remove from the oven and let cool completely. Remove the sides of the pan and slide the cake onto a serving plate. Cover with plastic wrap. Like crostata di ricotta, budino di ricotta needs to “age” before it is eaten in order for its flavor to develop. Refrigerate it for 2 days, then serve. It will keep, chilled, for up to 5 days.