Preheat your oven to 375 F of 190 C
In a large mixing bowl, mix together the blueberries, sugar, cornstarch, salt, cinnamon, and lemon juice.
Pour the mixture into one of the pie crusts.
Cut the butter into small pieces and sprinkle them over the blueberry mixture.
Place the second pie crust over the top of the blueberry mixture and crimp the edges with a fork.
Cut a few small slits in the top of the pie to allow steam to escape.
Bake the pie in the preheated oven for 50-60 minutes, or until the crust is golden brown and the filling is bubbling.
Let pie cool for at least 30 minutes.
