Make the tart dough: Pulse flour, sugar, and salt in a food processor. Add cold butter and pulse until mixture resembles coarse crumbs. Add egg yolk and ice water, pulsing just until dough comes together. Shape into a disk, wrap in plastic, and refrigerate for at least 1 hour.

Preheat oven to 375°F (190°C). Roll dough on a floured surface into a 12-inch circle. Fit into a 9-inch tart pan with removable bottom, pressing into corners. Trim excess dough, prick bottom with a fork, and refrigerate for 30 minutes.

Line the chilled shell with parchment paper and fill with pie weights or dried beans. Bake for 20 minutes, remove weights and parchment, then bake 10-12 minutes more until deep golden. Cool completely on a wire rack. Reduce oven to 325°F (165°C).

Prepare the custard: Combine heavy cream, milk, vanilla bean pod, and scraped seeds in a medium saucepan over medium heat. Bring just to a simmer, then remove from heat and let steep for 10 minutes. Remove vanilla pod.

Whisk egg yolks, sugar, cornstarch, and salt in a bowl until smooth and pale. Slowly pour the warm cream mixture into the yolk mixture while whisking constantly to temper the eggs.

Return the mixture to the saucepan and cook over medium-low heat, whisking constantly, until thickened enough to coat the back of a spoon, about 3-4 minutes. Do not let it boil.

Pour the custard through a fine-mesh strainer directly into the cooled tart shell, smoothing the top with an offset spatula.

Bake at 325°F for 25-30 minutes until the custard is set around the edges but still has a slight jiggle in the center (about the size of a quarter).

Cool the tart on a wire rack to room temperature, about 1 hour, then refrigerate for at least 3 hours or overnight until fully set.

Remove the tart from the pan by pushing up the bottom. Slice with a sharp knife, wiping the blade clean between cuts, and serve chilled or at cool room temperature.