01 - Pulse flour, powdered sugar, and salt in a food processor. Add cold butter and pulse until mixture resembles coarse crumbs. Add egg yolk and pulse. Drizzle in cold water, 1 tablespoon at a time, until dough just comes together.
02 - Turn dough onto a floured surface, shape into a disk, wrap in plastic, and refrigerate for at least 1 hour.
03 - Preheat oven to 350°F. Roll dough to fit a 9-inch tart pan. Press into pan and trim excess. Prick base with a fork.
04 - Line with parchment and fill with pie weights or dried beans. Bake 15 minutes. Remove weights and parchment; bake 10 more minutes until golden. Cool completely.
05 - Heat milk and vanilla bean (or extract) in a saucepan until just simmering. Remove from heat.
06 - Whisk egg yolks, sugar, and cornstarch in a bowl until smooth.
07 - Gradually whisk hot milk into egg mixture. Return to saucepan and cook over medium heat, whisking constantly, until thickened and bubbling (2-3 minutes). Remove from heat and stir in butter until smooth.
08 - Transfer to a bowl, cover with plastic wrap touching the surface, and refrigerate until cool (at least 1 hour).
09 - Spread cooled custard evenly in tart shell. Arrange fresh fruit decoratively over custard.
10 - Warm apricot jam and water in a small saucepan until melted. Strain if needed. Brush glaze gently over fruit for shine.
11 - Refrigerate assembled tart for 1 hour before serving for best results.