Preheat oven to 350°F if not already preheated.
In a large bowl, mix cream cheese, sugar, and cornstarch until smooth. Add sour cream, vanilla, and lemon zest, then mix until combined. Add eggs and mix until just combined.
Pour batter into prepared pan with crust. Spoon blueberry jam on top and swirl with a knife.
Bake for 38-42 minutes, then let cool in the oven with the door propped open for 10 minutes. Cool completely in the pan, then chill in the fridge for 6 hours.
Once cold, remove from pan, cut into squares, and enjoy!