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 necessary. Shape into a disk, wrap in plastic, and refrigerate for 30 minutes.
02 - Preheat oven to 350°F. Roll dough on floured surface and press into a 9-inch tart pan, trimming edges. Prick base with fork, line with parchment, and fill with pie weights. Bake 15 minutes, remove weights and parchment, then bake 10 minutes more until golden. Cool completely.
03 - Heat milk and split vanilla bean in saucepan until just simmering. Whisk egg yolks, sugar, and cornstarch until pale and thick. Gradually pour hot milk into yolk mixture while whisking constantly. Return to saucepan over medium heat, whisking until thick and bubbling for 2-3 minutes. Remove from heat, stir in butter, cover surface directly with plastic wrap, and chill.
04 - Spread cooled vanilla custard evenly over tart shell. Arrange fresh fruit decoratively on top. Warm apricot jam with water until liquefied and brush over fruit for glossy finish. Refrigerate 1 hour before serving.