Preheat oven to 425 degrees.
In a large bowl, mix sugar, flour, and cinnamon using a fork or whisk.
Gently toss the blueberries to coat with the flour mixture.
Spoon blueberry mixture into pastry-lined including any flour mixture that is left in the bowl.
Sprinkle the blueberry mixture with lemon juice and dot with pats of butter.
Cover with top crust.
Flute the edges and vent the pie crust. Simple cuts through the dough will suffice, or you can make a design. I like to add initials or simple cutouts to my pies.
Use a pastry brush and apply the egg wash to the top crust and the fluted edges of the pie.
Cover the pastry edge with aluminum foil strips and bake for 30 minutes. Remove foil and bake for an additional 15 minutes until pie top is a golden brown.