Preheat oven to 325°F. Line a 9x9-inch pan with parchment paper, leaving overhang. Set aside.
In a bowl, mix graham cracker crumbs, sugar, and melted butter until it looks like wet sand. Press firmly into pan bottom with the back of a measuring cup. Bake 10 minutes until set. Cool completely.
In a small saucepan, combine blueberries, sugar, lemon juice, and cornstarch. Cook over medium heat for 5 minutes, stirring until berries burst and mixture thickens slightly. Mash lightly with a fork. Let cool.
In a large mixing bowl, beat cream cheese and sugar with electric mixer on medium until smooth (2 minutes). Add eggs one at a time, beating just until blended. Mix in lemon juice, zest, and vanilla until creamy.
Pour filling over cooled crust. Spoon blueberry mixture in dollops over the top. Use a knife or toothpick to gently swirl for a marbled effect.
Bake 40 minutes until edges are set and center has a slight jiggle. Turn off oven, crack door, let cool inside 1 hour.
Refrigerate 4 hours or overnight until firm. Lift out using parchment, cut into bars.