Preheat your oven to 325°F (165°C). Line an 8×8-inch baking pan with parchment paper, leaving an overhang on the sides for easy removal. Lightly coat with non-stick spray.
In a medium bowl, combine graham cracker crumbs, sugar, melted butter, and cinnamon if using. Mix until the texture resembles wet sand. Press the mixture firmly and evenly into the prepared pan, creating a solid foundation about ¼-inch thick.
Bake the crust for 8-10 minutes until lightly golden. Remove from oven and allow to cool slightly while preparing the filling.
In a large mixing bowl, beat softened cream cheese until completely smooth (about 2-3 minutes). Add sugar and continue beating until fully incorporated. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract and lemon juice, mixing until just combined.
Pour the cream cheese mixture over the pre-baked crust, spreading evenly with a spatula. Give the pan a gentle tap on the counter to release any air bubbles.
In a medium saucepan, combine 1 cup of blueberries, sugar, cornstarch, water, and lemon zest. Cook over medium heat, stirring constantly until the mixture thickens (about 3-4 minutes). Remove from heat and gently fold in the remaining 1½ cups of blueberries.
Carefully spoon the blueberry mixture over the cream cheese layer, spreading gently to cover the surface.
Bake for 35-40 minutes, or until the center is almost set (it should have a slight jiggle). The internal temperature should reach approximately 150°F if you're using a food thermometer.
Allow the bars to cool at room temperature for 1 hour, then refrigerate for at least 2 hours before serving.