1. Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
2. In a mixing bowl, combine flour, sugar, and salt. Add cold butter and mix until the mixture resembles coarse crumbs.
3. Gradually add ice water, one tablespoon at a time, until the dough comes together. Form into a disk, wrap in plastic, and refrigerate for 30 minutes.
4. In another bowl, mix blueberries, sugar, cornstarch, lemon juice, and lemon zest.
5. Roll out the dough on a floured surface into a 12-inch circle. Transfer to the prepared baking sheet.
6. Spoon the blueberry mixture onto the center of the dough, leaving a 2-inch border. Fold the edges over the filling.
7. Brush the dough with milk and sprinkle with coarse sugar.
8. Bake for 40 minutes or until the crust is golden and the filling is bubbly. Let cool before serving.