Have ready a 9-inch pie pan with a removable bottom. In case you don't have a pie dish, you can use a springform pan for cakes. You'll come halfway up the sides with the crust, so it's roughly the same height as a pie.
Have ready 1 recipe for Italian Pie Crust. When ready to bake, roll the dough on a lightly floured counter until a few inches bigger than the pie plate. Carefully line the pan without stretching the dough and pinch the edges. You might need to cut a few overhanging pieces.
Prick the bottom and refrigerate or freeze (better) while you make the filling.
Preheat oven to 350ºF (180ºC).
For the filling:
Mix 1 pound whole-milk ricotta and gradually add ½ cup sugar and 1 tablespoon all-purpose or cake flour until creamy. You can do this by hand, it just needs to be well integrated.
Add 4 egg yolks, ¼ cup heavy cream, ¼ cup sour cream, 1 teaspoon vanilla extract, 1 tablespoon lemon zest, 1 teaspoon lemon juice and 3 tablespoons Marsala wine if using. Mix well.
Beat 4 egg whites with a pinch of salt until medium-firm peaks form, and add them in 2 parts to the ricotta mixture with a spatula. Integrate them until there are barely remains of beaten whites, but don’t mix too much and don't beat.
Pour into the cold pie shell and bake for 50-60 minutes, until the filling is almost firm and golden. It should barely jiggle in the middle.
Let cool completely on a wire rack.
It can be kept at room temperature for two days or refrigerated, well covered, for several days.
Notes
Ricotta: it might be watery as natural yogurt sometimes is. So you might need to drain it if that is the case. Simply put a colander with a cheesecloth over a bowl, add the ricotta and wait until the liquid has collected. Use it directly. If leaving it do drain overnight or for several hours, cover the bowl and refrigerate it. Creamy ricotta: this is a cheese that's supposed to be somewhat grainy, not completely smooth like cream cheese. But you can blend it or process it first to achieve a smoother consistency. Flavorings: Use almond extract in addition to the vanilla, and substitute the Marsala for hazelnut or orange liqueurs (like Frangelico, Cointreau or Grand Marnier).