Preheat the oven to 325 degrees. Spray a 9-inch square baking pan with cooking spray. Line the pan with foil, allowing several inches to hang over the edges. Spray the foil lightly with cooking spray and set pan aside.

Combine the graham cracker crumbs, sugar, butter, and salt in a mixing bowl and stir until the crumbs are evenly moistened. Press the mixture into the bottom of the prepared pan. Bake for 5 minutes.

Remove from the oven and let cool on a wire rack while you make the filling.

Combine the cream cheese and sugar in a medium mixing bowl and beat with an electric mixer on medium until very smooth. Add the flour and beat on low to combine; scrape down the sides and bottom of the bowl.

Beat in the eggs one at a time, then beat in the sour cream, vanilla, lemon zest (if using), and salt. Scrape down the sides and bottom of the bowl, then beat on low for a few more seconds.

Gently fold in the blueberries. Spread the filling over the crust and return the pan to the oven for 30 to 40 minutes, until the edges of the cheesecake are set but the center still jiggles.

Remove from the oven and run a knife around the edge of the pan. Set the pan on a wire rack to cool completely, then chill for at least 4 hours (or overnight).

Use the foil to remove the bars from then pan, then slice and serve.