Prepare Blueberry Sauce: In a medium saucepan, combine fresh blueberries, sugar, and lemon juice over medium heat. Gently mash the berries while they cook for about 5 minutes. Mix cornstarch with water until smooth, then stir it into the pan to thicken. Strain the mixture to remove skins and seeds, then let it cool.

Preheat Oven: Set your oven to 325°F (160°C) and allow it to preheat fully. Gather your muffin pan lined with cupcake liners.

Make Crust: In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted unsalted butter until resembling wet sand. Press into the bottom of each cupcake liner and bake for about 5 minutes until slightly golden. Let cool.

Mix Filling: In a large mixing bowl, beat room temperature cream cheese and sugar until smooth, adding lemon juice, zest, vanilla, and eggs one at a time, blending on low.

Assemble: Once the crusts have cooled, fill each cup with cheesecake filling until two-thirds full and spoon cooled blueberry sauce on top, swirling for a marbled effect.

Bake: Bake for 17-20 minutes until tops are set with a slight jiggle in the center. Avoid opening the oven door.

Cool & Chill: Let cool at room temperature for 1 hour, then refrigerate for at least 3-4 hours or overnight.