Preheat oven to 350°F (175°C). Mix cracker crumbs, 1/4 cup sugar, and melted butter. Press into a 9-inch springform pan and bake 10 minutes. Cool.

Lower oven to 325°F (160°C). Beat cream cheese and 1 cup sugar until smooth, 2 minutes. Blend in sour cream and vanilla. Add eggs one at a time on low, then fold in flour by hand.

Cook blueberries, 1/4 cup sugar, and lemon juice on medium heat for 5-7 minutes until berries burst. Stir in cornstarch slurry and cook 1-2 minutes until thick. Cool 10 minutes.

Spread half the filling over the crust. Dollop half the sauce and swirl with a knife for 10 seconds. Top with remaining filling, then the rest of the sauce, and swirl once more.

Place pan on a baking sheet. Bake at 325°F (160°C) for 50-60 minutes until edges are set and center jiggles slightly. Turn off oven, crack door, and leave inside 1 hour. Cool to room temp, then chill at least 4 hours.

Run a knife around the edge, remove the ring, and slice with a hot, dry knife.