01 - Combine flour, sugar, and salt in a bowl. Cut in cold butter until mixture resembles coarse crumbs. Add egg yolk and 2 tablespoons cold water, mixing gently until dough just comes together (add more water if needed). Shape into a disk, wrap in plastic, and refrigerate for 30 minutes.
02 - Preheat oven to 350°F. Roll dough out on a floured surface and press into a 9-inch tart pan. Trim edges. Prick base with a fork, line with parchment, and fill with pie weights or beans. Bake for 15 minutes, remove weights and parchment, then bake 10 minutes more until golden. Cool completely.
03 - Heat milk and split vanilla bean (or extract) in a saucepan until just simmering. Whisk egg yolks, sugar, and cornstarch in a bowl until pale and thick. Gradually pour hot milk into yolk mixture, whisking constantly. Return mixture to saucepan over medium heat, whisking until thick and bubbling for 2–3 minutes. Remove from heat, stir in butter. If using vanilla extract, add now.
04 - Transfer custard to a bowl, cover with plastic wrap directly on surface, and chill until completely cooled.
05 - Spread cooled vanilla custard evenly over tart shell. Arrange fresh fruit decoratively on top.
06 - Warm apricot jam with 1 tablespoon water until liquefied. Brush over fruit for a glossy finish. Refrigerate 1 hour before serving.