This tender cake, sometimes referred to as a pudding (budino di ricotta) started out as a pancake. Food historian Clifford Wright notes that Sicilian Jews took their traditions of making and cooking with ricotta to Rome when they were expelled from Sicily in the 15th century, and a version of this recipe came with them. You can still find this delicious dessert in Rome's Jewish quarter in its simplest form — eggs, sugar, ricotta, and cinnamon. In our recipe, we separate the eggs and fold in the beaten whites, which make the cake even more delicate. If you can't find good quality fresh ricotta, make your own.
Preheat the oven to 350 degrees. Grease the bottom and sides of a 9-inch springform pan with the butter, then dust the pan with the breadcrumbs.
Beat the egg yolks with the sugar, flour, salt, and cinnamon in a large mixing bowl with an electric mixer until creamy, about 5 minutes. Process the ricotta, Grand Marnier, and zest in a food processor until smooth. Fold the ricotta into the egg mixture, using a rubber spatula, until the batter is well mixed.
In another mixing bowl, beat the egg whites with a whisk, or an electric mixer fitted with a whisk, until frothy. Add a little squeeze of lemon juice and continue to beat until the whites are stiff but not dry. Fold 1/3 of the whites into the batter, then gently fold in the remaining whites, in 2 batches, taking care not to overmix, which will cause the whites to deflate.
Pour the ricotta batter into the prepared pan. Bake until golden and firm to the touch, about 40 minutes. Remove the cake from the oven and transfer to a rack. It will sink as it cools. This cake is best served warm or at room temperature. It loses a little flavor when it is refrigerated.