Place bottom crust into pie plate, prick the bottom a few times with a fork.
Combine sugar, flour and cinnamon in a large bowl.
Fold in blueberries, turning to coat.
Pour blueberries into pie plate, and sprinkle extra dry mixture evenly over blueberries.
Dot with chopped butter or margarine and sprinkle lemon juice on top.
Place remaining pie crust on top, seal and flute edges.
For a flakier crust, whisk an egg yolk in a small bowl, mix in about a teaspoon of water and brush lightly on top of pie crust.
Slit the top crust a few times for steam to escape.