Preheat oven to 325°F.
Mix crushed crackers, butter, and sugar.
Press mixture into springform pan bottom.
Beat cream cheese until smooth and fluffy.
Add sugar gradually while mixing continuously.
Beat in eggs one at a time.
Mix in vanilla and sour cream.
Pour filling over prepared crust evenly.
Bake for 45-50 minutes until center sets.
Cool completely before removing from pan.
Cook blueberries, sugar, and cornstarch together.
Stir until mixture thickens into dark sauce.
Add lemon juice and cool completely.
Spread blueberry topping over cooled cheesecake.
Refrigerate for at least 4 hours.