Preheat the oven to 325 and position a rack in the middle. Lightly grease a 9-inch springform pan with butter or non-stick cooking spray, dust it with flour, and tap to knock out the excess.

To make the crust: Place the almonds, flour, sugar, and salt in a food processor and process until the nuts are finely chopped. In a small bowl, lightly whisk together the egg yolk, melted butter, and vanilla extract. Add the liquids to the nut mixture and pulse several times to moisten and combine the ingredients thoroughly. The mixture should come together easily between your fingers when pinched.

To form the crust, press the mixture onto the bottom and about an inch up the sides of the springform pan. Place the pan in the refrigerator for 15 to 20 minutes to firm up the crust, then bake for 10 to 15 minutes, or until the crust is light golden brown. Remove the pan from the oven and allow the crust to cool completely on a wire rack.

To make the filling: In an electric mixer fitted with the paddle attachment, beat the cream cheese with the sugar and salt on medium speed until soft and creamy, about 1 minute. Add the ricotta and beat until the mixture is smooth and light, another 2 minutes. Beat in the eggs, one at a time, scraping down the sides of the bowl with a spatula. Beat in the vanilla extract, amaretto, and cornstarch. Fold in the candied fruits, if desired, with the spatula.

Pour the filling into the cooled crust, smoothing the top with the spatula. Bake the cheesecake for 45 to 50 minutes, or until the center is set; it should be jiggly but not liquid. Remove the cheesecake from the oven and allow it to cool completely in the pan onn a wire rack.

Chill the cooled cheesecake for at least 4 hours before serving; it is best served fully chilled on the following day. To serve, remove the sides of the springform pan and cut the cheesecake into wedges with a long, thin-bladed knife. Any leftover cake should be wrapped in plastic and stored in the refrigerator for up to 3 days.