Preheat your oven to 475°F (245°C).

In a food processor, pulse flour and sugar until combined. Gradually add cold butter until mixture resembles coarse crumbs.

In a bowl, whisk together egg and cold water. Stream this mixture into the food processor while blending until dough forms.

On a floured surface, fraisage the dough until smooth. Shape into a disc, wrap in plastic, and chill for 15 minutes.

Roll out the dough until large enough for a tart pan, transfer it to the pan, and trim excess. Poke small holes in the bottom.

Sprinkle corn starch and sugar across the tart shell. Arrange apricot halves skin-side down on top.

Bake on the lowest rack for 10 minutes at 475°F, then reduce heat to 425°F (220°C) and bake for another 30 minutes.

Once baked, cool on a wire rack and brush apricots with apricot jam mixed with water.