1. Begin by preparing the pastry. Combine flour, sugar, and salt in a mixing bowl, work in the cold butter using a pastry cutter or fingers until the mixture resembles coarse crumbs.
2. Mix cold water and cider vinegar, then gradually add to the flour mixture until it forms a dough. Gather it into a ball, flatten into a disc, wrap, and refrigerate for at least 30 minutes.
3. Prepare the apricot filling by cutting the apricots and mixing them with sugar, vanilla bean seeds, and a pinch of salt in a bowl. Toss gently to coat evenly.
4. Roll out the refrigerated pastry dough on a floured surface into a 30cm (12 inches) diameter disc. Work quickly to keep the dough cold and transfer it to a lined baking sheet.
5. Place the apricot filling in the center of the rolled-out dough, leaving a 5cm (2 inches) border. Fold the edges of the dough over the filling while pleating gently, ensuring the center remains exposed.
6. Chill the assembled galette in the fridge for 15 to 30 minutes to allow the dough to firm up.
7. Preheat the oven to 200°C (400°F). Brush the edges of the dough with an egg wash and sprinkle granulated sugar over them for added texture.
8. Bake the galette in the preheated oven for 35 to 50 minutes, or until the crust is golden brown and the apricot filling is bubbling. Lower the oven temperature to 350°F in the last 10 to 20 minutes for an even bake.
9. Allow the galette to cool slightly once removed from the oven to let the flavors develop fully.
10. Serve warm or at room temperature. Pair it with a scoop of vanilla ice cream, whipped cream, or crème fraîche for an indulgent dessert experience.