Preheat your oven to 425°F (220°C).
In a mixing bowl, combine flour and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Gradually add ice water, tossing with a fork until dough holds together when pressed. Divide dough in half. Shape each into a disk; wrap and refrigerate for at least 1 hour.
On a lightly floured surface, roll out one half of the dough to fit a 9-inch pie dish. Transfer dough to pie dish. Trim even with edge.
In a large bowl, combine blueberries, sugar, cornstarch, lemon juice, lemon zest, and vanilla extract. Pour into crust; dot with butter.
Roll out remaining dough to fit top of pie; place over filling. Trim, seal, and flute edges. Cut slits in top. If desired, brush with milk and sprinkle with sugar.
Bake for 50-60 minutes or until crust is golden brown and filling is bubbly. Cool on a wire rack.