To prepare a crostata with lemon custard and whipped ricotta cream recipe, first you need to prepare the graham cracker crust. Preheat the oven to 375?F (190?C) and grease the bottom and sides of an 8-inch (20.32-centimeter) square baking dish. Place the crackers in the dish and bake for 10 to 12 minutes, or until they are lightly browned. Remove the crust and set aside to cool. Using an electric mixer, beat the egg whites until stiff peaks form. Gradually add the sugar, beating well after each addition. Add the vanilla and the lemon zest and beat until the mixture is light and fluffy, about 2 minutes. Pour the batter into the prepared dish, and sprinkle the top with shredded coconut. Bake for 20 to 25 minutes until it is golden brown. Serve warm or at room temperature.