8 tbsp unsalted butter – cut into 0.5-inch cubes, chilled
4 tbsp ice water
1.5 pounds nectarines – pitted and sliced 0.5-inch thick
0.5 cups granulated sugar
1 tbsp lemon juice
0.125 tsp fine sea salt
3 tbsp cornstarch
2 tbsp almond flour – sprinkled on dough base
1 large egg – beaten (for egg wash)
1 tbsp milk – for egg wash
2 tbsp turbinado sugar
Instructions
Whisk the all-purpose flour, 1 tbsp granulated sugar, and 0.25 tsp fine sea salt in a large bowl.
Cut in the chilled unsalted butter with a pastry cutter or fingertips until the mixture has pea-size bits of butter.
Sprinkle in the ice water, 1 tbsp at a time, tossing just until the dough holds together when pressed. Gather into a 1-inch-thick disk, wrap, and chill until firm, about 1 hour.
In a medium bowl, combine the sliced nectarines, 0.5 cup granulated sugar, lemon juice, and 0.125 tsp fine sea salt. Toss and let macerate until juicy, 15–20 minutes.
Stir the cornstarch into the nectarine mixture until no dry pockets remain.
Heat the oven to 400°F (200°C). Line a rimmed baking sheet with parchment.
Roll the chilled dough between two sheets of parchment into a 12-inch round about 1/8 inch thick. Peel off the top sheet and transfer the dough (on the bottom parchment) to the baking sheet.
Sprinkle the almond flour evenly over the center, leaving a 2-inch border.
Spoon the nectarine mixture over the almond flour, spreading in an even layer and leaving a 2-inch border. Fold the dough edges up and over the fruit, pleating as needed.
Beat the egg with the milk. Brush the crust with the egg wash and sprinkle the turbinado sugar over the crust.
Chill the assembled galette until the dough is slightly firm, 10–15 minutes.
Bake until the crust is deep golden and the fruit juices are bubbling and thickened, 40–50 minutes. If the crust browns too quickly, tent the edges loosely with foil.
Cool on the sheet for 10 minutes, then slide the galette (with parchment) onto a rack to cool further. Serve warm or at room temperature.