Preparation

• Preheat the oven to 450°F/232°C and prepare the cake pan. Butter a 9-inch (23cm) springform pan and line it with parchment paper on the bottom and sides.
• Make the shortbread crust. In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, sugar, vanilla, and salt on medium speed until well combined and light in color. Blend in the flour on low speed just until the mixture holds together when squeezed.
• Add the crust to the cake pan. Press the shortbread mixture evenly around the bottom and slightly up the sides of the springform pan. Refrigerate while making the filling.
• Make the apple topping. Add all of the apple topping ingredients to a skillet and sauté until tender yet still firm (about 10 to 12 minutes). Remove to a bowl and allow to cool slightly.
• Make the mascarpone filling. In the bowl of a stand mixer fitted with the whisk attachment, whisk mascarpone on medium speed until light and fluffy (about 2 to 3 minutes). Add sugar, vanilla, lemon juice, and salt and blend well (about 1 minute more). Add the egg and beat just until no streaks remain (about 15 seconds).
• Assemble the torte and bake. Add the mascarpone filling to the crust, top with the apple mixture, and lightly press down. Bake at 450°F/232°C for 10 minutes, then reduce heat to 400°F/204°C and continue baking for 20 to 25 minutes until golden brown. Cool for 15 minutes in the pan, then finish cooling on a wire rack.