Make the dough: In a bowl, whisk flour, sugar, and salt. Cut in cold butter with a pastry cutter or fingertips until it looks like coarse crumbs. Stir in egg yolk and just enough ice water to form a shaggy dough.

Chill: Press into a disk, wrap, and chill 30 minutes. This helps the crust stay crisp and prevents shrinking.

Roll and fit: On a lightly floured surface, roll to about 1/8 inch thick. Fit into a 9-inch tart pan with removable bottom. Trim edges. Prick base with a fork and freeze 10 minutes.

Blind-bake: Line with parchment and fill with pie weights or dried beans. Bake at 375°F (190°C) for 15 minutes. Remove weights and parchment; bake 8–10 more minutes until golden. Cool completely.

Whip the filling: Beat mascarpone, cream cheese, powdered sugar, vanilla, and lemon zest until smooth. In a separate bowl, whip cold heavy cream to soft peaks. Fold whipped cream into the mascarpone mixture until silky.

Fill the shell: Spread the filling into the cooled crust. Smooth the top with an offset spatula. Chill 30–45 minutes to set slightly.

Prep the berries: Pat berries dry. If using strawberries, slice them. Warm jam with a splash of lemon juice until glossy; cool briefly.

Top and glaze: Arrange berries in circles or clusters. Brush lightly with the jam to add shine and keep fruit fresh.

Chill and serve: Refrigerate at least 1 hour before slicing. Use a sharp knife and wipe between cuts for clean slices.