Preheat oven to 350° F. Spray a 9 x 11" baking dish with non-stick coating and then line with parchment paper that hangs over the sides of the dish. Apply a coating of non-stick spray to the parchment paper.
Using a food processor, add the butter, sugar, flour, cinnamon and salt. Process the mixture until it starts to clump, about 1 minute. Remove and reserve ¾ cup of the contents and then press mixture evenly into the baking dish and then set aside.
for the filling
Using a medium bowl, whisk the egg, sour cream, granulated sugar, lemon juice, all-purpose flour, cornstarch, vanilla and the cinnamon. Gently stir in 1 ½ cups of the blueberries. Pour filling mixture over the crust mixture. Evenly distribute the remaining blueberries over the filing.
Sprinkle remaining crust over blueberry filling, distribute evenly and gently pat. Bake for 1 hour and allow to cool on wire rack before serving. Dole out generous scoops of vanilla ice cream if desired.