1. Prepare the pie crust dough and chill according to your recipe or package directions (at least 2 hours or up to 5 days refrigerated).
2. In a large bowl, mix blueberries with sugar, flour, cornstarch, cinnamon, lemon juice, and lemon zest until the filling is evenly moistened and no longer powdery; some berries may burst slightly to release juice.
3. Preheat the oven to 425°F (218°C) and position the oven rack on the lower third; place a baking sheet on the bottom rack to catch spills.
4. Roll out one disc of chilled dough to a 12-inch circle and fit it into a 9-inch round pie dish, smoothing it to the edges.
5. Pour the blueberry filling evenly into the crust and dot filling with the cold butter cubes.
6. Roll out the second dough disc to 12 inches and either cut into strips for a lattice top or cover fully for a double crust. If using a full top crust, cut slits to allow steam to escape.
7. Assemble the top crust or weave strips in a lattice pattern over the filling, seal, trim excess dough, and crimp edges with a fork or decorative pattern.
8. Brush the top and edges with egg wash and optionally sprinkle with coarse sugar.
9. Bake at 425°F (218°C) for 25 minutes to set the crust and activate thickening. Then reduce oven temperature to 375°F (190°C), protect crust edges with foil or a pie shield, and bake an additional 40–50 minutes until the filling is bubbly throughout and reaches about 200°F (93°C) internally. (If using frozen berries, add extra baking time as needed.)
10. Remove pie from oven and cool on a rack for at least 4 hours before slicing to allow the filling to set firmly.