Preheat oven to 400 degrees. Roll pie crust to a diameter of 10 inches and place in the bottom of a 10-inch pie plate.

In a medium bowl, combine sour cream, egg, sugar, vanilla, 2 Tbsp. flour, and salt. Fold in blueberries. Pour the mixture into the pie crust. Bake 25 minutes. (You may want to cover the edges with foil or a crust shield to prevent excessive browning.)

In the meantime, prepare streusel: in a small bowl, combine brown sugar and flour, then work the butter in with a fork or your fingers. Stir in pecans.

After 25 minutes of baking, sprinkle streusel over the top of the blueberry filling. Return to oven and bake an additional 15-20 minutes until the filling is no longer jiggly and the topping is nicely browned. Cool 30 minutes before serving, or serve chilled.