Preheat your oven to 350°F (175°C). Grease a 9x9 inch baking pan with cooking spray or butter. Line it with parchment paper, allowing some overhang on the sides for easy removal later.
In a medium bowl, mix together the graham cracker crumbs and melted butter until the crumbs are well coated. Firmly press this mixture into the bottom of your prepared baking pan to create a solid crust. Bake in the preheated oven for 8-10 minutes until lightly golden, then remove and allow it to cool completely.
In a large mixing bowl, beat the softened cream cheese and granulated sugar with an electric mixer on medium speed until the mixture is smooth and creamy, about 2-3 minutes. Ensure there are no lumps.
Add the eggs one at a time, beating well after each addition to incorporate them fully. Then, add the vanilla extract, lemon zest, and lemon juice, mixing until everything is evenly combined.
In a small bowl, toss the fresh blueberries with cornstarch to coat them evenly. Gently fold the blueberries into the cheesecake mixture until they are distributed throughout.
Carefully pour the cheesecake filling over the cooled crust, smoothing it out into an even layer with a spatula.
Bake in the preheated oven for 30-35 minutes, or until the edges are set and the center has a slight jiggle. Keep an eye on them to avoid over-baking.
Once baked, remove the cheesecake bars from the oven and let them cool to room temperature. After they have cooled, refrigerate for at least 4 hours, but ideally overnight, to set properly and enhance the flavors.
After chilling, lift the bars out of the pan using the parchment paper overhang and transfer them to a cutting board. Slice into squares or rectangles as desired.
Serve the cheesecake bars garnished with additional fresh blueberries and a light dusting of powdered sugar, if you wish, for a lovely presentation.
Notes
For best flavor, refrigerate overnight before serving.