Mix flour, sugar, and salt together in a medium bowl
Grate cold butter and toss with flour, then work into dry ingredients until mixture resembles coarse breadcrumbs
Whisk together egg yolk, vanilla, and milk, then add to flour mixture and stir until crumbly
Fold dough over itself and gently knead until it just comes together
Chill dough for 2 hours if too soft, then roll out and form into tart shell
Poke holes with fork and bake at 375°F for 15-20 minutes until golden brown
Combine milk and vanilla bean in saucepan and bring to simmer, then steep for 10 minutes
Whisk together egg yolks, sugar, cornstarch, and salt, then mix in heavy cream
Slowly ladle warm milk mixture into yolk mixture while whisking constantly
Pour tempered mixture back into saucepan and cook over medium heat, whisking continuously, until thickened and bubbling (3-5 minutes)
Remove from heat and whisk in butter until silky
Strain custard through fine mesh sieve into tart shell
Arrange fresh berries on top of custard
Sprinkle gelatin over lemon juice and let sit for 3-5 minutes
Combine hot water and sugar in heatproof bowl and stir until dissolved
Add bloomed gelatin to hot sugar water and stir until fully melted
Cool glaze until just warm and pourable
Gently spoon or brush glaze over fruit, coating evenly
Refrigerate tart for at least 15-20 minutes to set glaze
