Preheat the oven to 350 degrees. In a medium sized mixing bowl, combine the flour, sugar, salt, and cinnamon. Mix the melted butter into the flour mixture. Add the eggs, one at a time and mixing until the eggs are thoroughly incorporated. Mix in the buttermilk and vanilla and set the filling aside.

Toss the rinsed blueberries or thawed and drained blueberries with 1 Tablespoon of flour and place the blueberries in the pie crust. Discard any remaining flour. Pour the buttermilk filling over the blueberries and gently push any berries that rise to the top back under the surface of the filling.

Cover the edges of the pie with aluminum foil or with a pie crust shield and place on the middle rack of the oven. Bake at 350 degrees for 45 minutes. After 45 minutes remove the aluminum foil or shield. Continue baking for another 10-15 minutes or until the pie is evenly golden brown across the top and set in the middle. 

Remove to a wire cooling rack and cool completely. Place in the refrigerator until ready to serve.