Preheat the oven to 350 degrees F.

Spray an 8-by-8-inch baking pan with cooking spray. Line the pan with parchment paper so that it hangs over on two sides. Spray the parchment.

For the crust: In the bowl of a food processor, combine the butter, sugar, flour, cinnamon and salt. Process until the mixture starts to come together and clump, 1 minute. Remove 3/4 cup and reserve; press the remaining crust mixture evenly into the prepared baking pan. Set aside.

For the filling: In a medium bowl, whisk together the egg, sour cream, sugar, lemon juice, flour, cornstarch, vanilla extract and cinnamon until smooth. Mix in 1 cup of the blueberries. Pour the filling mixture over the crust, shaking the pan gently to settle the custard and berries. Pour the remaining 1 cup blueberries over the top, spreading them evenly.

Take the reserved crust and sprinkle it over the top of the berries, squeezing the mixture in your hands to encourage large lumps.

Bake for 1 hour. Let cool. Remove the bars from the pan and cut into 9 pieces. Refrigerate until ready to serve.