Cream the soft butter with the sifted powdered sugar. Add the salt, vanilla seeds, and almond flour.
Mix well, scraping down the bottom of the bowl. Incorporate the beaten egg, mix gently with a spatula, then bring everything together using a stand mixer.
Next, add the sifted flour and mix briefly, without kneading or forming a ball, you want to avoid overworking the dough.
Turn the dough out onto your work surface and press it down and smear it lightly with the palm of your hand to bring it together evenly.
Form the dough into a ball, divide it in two, wrap each piece in plastic wrap, and refrigerate, preferably overnight.
The next day, take the dough out, let it soften slightly, then roll it out to about 3 mm thickness. Line your tart ring with the dough.
Bake for 15 minutes in a preheated oven at 150°C (300°F) with fan (convection mode) or 170°C (340°F) without fan (conventional oven).
You can also skip the blind-baking step if you’re worried the edges might collapse during baking.
Otherwise, once the tart shell is pre-baked, you can fill it directly while still in the tart ring. Alternatively, unmold the shell after baking, let it cool slightly, and smooth the edges with the back of a sieve before filling.
Brush a thin layer of egg wash over the tart shell before adding the almond and pistachio cream.