Preheat your oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper, leaving some overhang on the sides for easy removal.
For the crust: In a mixing bowl, combine gluten-free flour, powdered sugar, and a pinch of salt. Add melted butter and mix until a dough forms. Press the dough evenly into the bottom of the prepared pan. Bake the crust in the preheated oven for 20 minutes, or until lightly golden brown. Remove from the oven and set aside to cool slightly.
For the filling: In a separate mixing bowl, beat 16 ounces of softened cream cheese until smooth. granulated sugar, eggs, lemon juice, vanilla extract and the zest of one lemon. Mix until well combined.
Assemble: Add half the blueberries to the crust evenly and pour the cream cheese mixture over the baked crust and spread it out evenly. Add the additional fresh blueberries evenly over the top of the filling.
Return to oven: Place the pan back in the oven and bake for 25-30 minutes, or until the edges are set and the center is just slightly jiggly. If you are using a 9x9 pan, you will need to increase cook time to 35-40 minutes.
Cool: Remove the pan from the oven and allow the bars to cool completely at room temperature, then refrigerate for at least 2 hours or until chilled and set.
Chill & Slice: Once chilled, use the parchment paper overhang to lift the bars out of the pan and onto a cutting board. Slice into squares and serve. Optionally, garnish with additional lemon zest or a sprinkle of powdered sugar before serving.