Preheat the oven to 350°F (175°C). Grease an 8x8 inch baking dish or line it with parchment paper for easy removal.
In a mixing bowl, combine the graham cracker crumbs, 1/4 cup sugar, and melted butter. Mix well until the crumbs are moistened.
Press the mixture evenly into the bottom of the prepared baking dish to form the crust layer. Bake for 10 minutes, then remove from the oven to cool slightly.
In another bowl, beat the softened cream cheese and 1 cup sugar together until smooth and creamy, about 2-3 minutes.
Add in the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract, lemon zest, and lemon juice until just combined.
Gently fold in the fresh blueberries, being careful not to break them.
Pour the cheesecake filling over the cooled crust and spread evenly. Bake for 25-30 minutes, or until the center is set and no longer jiggly.
While the cheesecake is baking, prepare the topping. In a small saucepan over medium heat, combine the fresh blueberries, 1 tablespoon sugar, lemon juice, and cornstarch. Cook until the mixture is bubbly and thickened, about 5 minutes. Remove from heat and let cool.
Once the cheesecake is done, remove from the oven and let it cool to room temperature, then refrigerate for at least 3 hours or until fully chilled.
Once chilled, spread the blueberry topping over the cheesecake bars. Cut into squares and serve chilled or at room temperature.
Notes
For best results, chill the bars for at least 3 hours before serving.