Whisk together flour, 1 tablespoon sugar, and salt and in medium bowl.

Add cold butter and cut it into the flour using a pastry cutter or your fingertips until the mixture resembles coarse crumbs with pea-size pieces of butter.

Stir in one egg.

Add ice water, mixing gently until the dough begins to come together.

Form the dough into a disk, wrap tightly in plastic wrap, and refrigerate for at least 1 hour.

Combine the blueberries, sugar, cornstarch, lemon zest, lemon juice, and salt in a medium bowl.

Toss gently to coat and set aside while you roll the dough.

Preheat the oven to 400°F. Line a baking sheet with parchment paper.

On a lightly floured surface, roll the chilled dough into a 12-inch circle, about ⅛ to ¼ inch thick. Transfer to the prepared baking sheet.

Spoon the blueberry filling into the center of the dough, leaving a 2-inch border around the edges.

Fold the edges of the dough over the fruit, pleating as you go to create a rustic border.

Beat remaining egg. Brush the crust with the beaten egg and sprinkle with remaining sugar.

Bake for 35–40 minutes, or until the crust is deep golden.

Allow the galette to cool for at least 30 minutes before slicing. Serve warm or at room temperature.