Set oven to 400°F (200°C).
Fit one crust into a 9-inch pie plate.
In a bowl, toss blueberries with sugar, cornstarch, lemon juice, zest, and cinnamon until evenly coated.
Pour filling into crust and dot with butter.
Roll out second crust, cut strips, and weave into a lattice design.
Seal edges and brush top with egg wash.
Bake at 400°F for 20 minutes. Lower to 350°F (175°C) and bake an additional 30 minutes, or until crust is golden and filling bubbly.
Let pie cool 2 hours before slicing to allow filling to set. Serve with ice cream or whipped cream.