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 additional water only if needed to form dough.
02 - Shape dough into a disk, wrap in plastic wrap, and refrigerate for 30 minutes to firm.
03 - Preheat oven to 350°F. Prepare a 9-inch tart pan by lightly greasing if necessary.
04 - Roll chilled dough on a floured surface and press into the tart pan. Trim edges evenly.
05 - Prick base with a fork, line with parchment paper, and fill with pie weights or dried beans. Bake for 15 minutes, remove weights and parchment, then continue baking 10 minutes until golden brown. Cool completely.
06 - In a saucepan, heat whole milk with split vanilla bean (or extract) until just simmering.
07 - Whisk egg yolks, sugar, and cornstarch in a bowl until pale and thickened.
08 - Gradually pour hot milk into yolk mixture while whisking constantly. Return mixture to saucepan over medium heat, whisking continuously until thickened and bubbling, about 2-3 minutes.
09 - Remove from heat, stir in butter and vanilla extract if using. Transfer to a bowl, cover with plastic wrap directly on surface to prevent skin, and refrigerate until completely cooled.
10 - Spread cooled vanilla custard evenly over the completely cooled tart shell.
11 - Arrange mixed fresh fruit decoratively over the custard in a pattern of your choice.
12 - Warm apricot jam with 1 tablespoon water in a small saucepan or microwave until liquefied.
13 - Brush warm apricot glaze over fruit for a glossy, professional finish. Refrigerate assembled tart for at least 1 hour before serving to set.