In a stand mixer fitted with the paddle attachment (or a food processor), combine the flour, caster sugar, vanilla sugar, and salt. Blend briefly to ensure even distribution of flavors.

Add the cold, cubed butter to the dry mixture. Pulse or mix on medium speed until the mixture resembles wet sand with small, even granules. This step creates the sandy texture essential for a tender, crumbly crust.

Mix in the egg yolk and almond flour. Blend until the dough forms a smooth, cohesive ball that pulls away from the bowl. If the dough feels slightly sticky, sprinkle in a little extra flour, but avoid overmixing to maintain a light texture.

Shape the dough into a flat disk, wrap it tightly in plastic wrap, and refrigerate for 30 minutes to 1 hour. Chilling firms up the butter and makes the dough easier to roll out.

Place the chilled dough between two sheets of parchment paper. Roll it out gently to a thickness of 3–4 mm, ensuring an even layer for consistent baking.

Transfer the rolled dough to a tart pan (28–30 cm in diameter). Adjust the edges neatly and trim off the excess dough by rolling a pin over the pan’s edges. Prick the base with a fork to prevent puffing during baking.

Cover the dough with parchment paper and fill it with baking beads, dried beans, or rice to keep it from rising. Bake in a preheated oven at 180°C (356°F) for 20 minutes to partially cook the crust.

Remove the weights and parchment paper, then return the tart shell to the oven. Bake for an additional 10 minutes, or until the base is golden and crisp.