Heat oven to 325°F. Line an 8-inch square pan with a parchment sling.
Combine blueberries, sugar, lemon juice, and 2 tablespoons water in a small saucepan.
Simmer over medium heat until berries burst, 4 to 5 minutes.
Whisk cornstarch with remaining 1 tablespoon water. Stir into berries and cook until glossy and thick. Cool.
Stir crumbs, crust sugar, salt, and crust zest in a bowl. Add melted butter and mix until evenly moistened.
Press crust firmly into the pan. Bake 8 to 10 minutes, then let cool slightly.
Beat cream cheese and filling sugar until smooth and fluffy, about 1 minute.
Mix in sour cream, filling zest, vanilla, lemon juice, and flour until just combined.
Beat in eggs one at a time on low speed. Avoid overmixing.
Pour filling over warm crust. Spoon blueberry mixture on top and swirl gently with a knife.
Bake 30 to 35 minutes, until edges are set and center still slightly wobbly.
Cool to room temperature. Chill at least 3 hours until firm, then slice into bars.
Notes
Variation: Swap in raspberries or blackberries for the swirl, or add 1 tsp poppy seeds to the crust for crunch. Storage: Keep refrigerated up to 4 days or freeze, well wrapped, for 2 months. Serve chilled with extra lemon zest on top.This recipe is an original creation inspired by classic Blueberry Lemon Cheesecake Bars flavors. All ingredient ratios and instructions are independently developed.