Limoncello Mascarpone Tart

1. For the crust: In a food processor, combine flour, butter, and granulated sugar. Pulse until mixture resembles coarse crumbs. 2. Add egg yolk and ice water, 1 tablespoon at a time, pulsing until dough comes together. Form into a disc, wrap, and chill for 30 minutes. 3. Preheat oven to 375°F (190°C). Roll out dough and press into a 9-inch tart pan. Prick bottom with a fork. 4. Bake for 20-25 minutes, or until lightly golden. Let cool completely on a wire rack. 5. For the filling: In a bowl, whisk together mascarpone cheese, powdered sugar, limoncello, and lemon zest until smooth and creamy. 6. Spread the mascarpone filling evenly into the cooled tart shell. 7. Chill for at least 2 hours before serving. Garnish with additional lemon zest if desired.