Make Blueberry Sauce: In a saucepan over medium heat, combine blueberries, sugar, and lemon juice. Cook until the berries soften, mashing them gently. Stir in cornstarch mixed with water and cook until thickened, around 5 minutes.

Prepare the Crust: Preheat your oven to 325°F. In a bowl, mix graham cracker crumbs with sugar and melted butter. Press this mixture firmly into cupcake liners in a muffin pan. Bake for 5 minutes until lightly golden, then allow to cool.

Blend the Cheesecake Filling: In a mixing bowl, beat room temperature cream cheese and sugar until creamy and smooth. Add the lemon juice, zest, and vanilla extract. Incorporate eggs one by one at low speed, mixing just until combined to avoid overmixing.

Assemble the Cheesecakes: Spoon the cheesecake batter into the cooled crusts, filling each about two-thirds full. Add a generous dollop of blueberry sauce on top and swirl gently using a toothpick or knife. Bake for 17-20 minutes, until the sides are set and the center is slightly jiggly.

Cool and Chill: Allow the cheesecakes to cool at room temperature for 1 hour. Place them in the refrigerator for at least 3-4 hours, or until fully set, before serving.