Preheat oven to 375°F.
Roll out the crust: Line a baking sheet with parchment paper. On a floured surface, roll out the pie dough into a 12-inch circle. Place the pie dough on the baking sheet.
Make the Filling: In a medium bowl, combine the granulated sugar with lemon zest. Rub together until the sugar seems damp. Add the cornstarch and stir to combine. Gently stir in the blueberries.
Assemble the Galette: Place the blueberries onto the pie dough, leaving about a one-inch border around the edge.
Fold edge of dough over the blueberries, pleating as needed. If the dough tears, pinch it back together. If desired, sprinkle sugar over the edges of the dough.
Bake the Galette: Bake until the filling bubbles and the crust is golden brown, about 40 minutes. Allow the galette to cool for about 15 minutes before serving.
Store the galette in the refrigerator for up to three days.