Preheat oven to 350°F. Place a pan of water on the bottom rack. Line a 9-inch springform pan with parchment. Mix graham crumbs, sugar, and butter. Press into base and bake 8–10 minutes. Cool.

Beat cream cheese and sugar until smooth. Add sour cream, lemon juice, zest, and flour. Mix gently. Add eggs one at a time without overmixing. Pour filling over crust.

Bake 50–60 minutes until edges set and center jiggles slightly. Turn oven off, crack door, and cool 10–15 minutes. Cool fully on a rack, then refrigerate 6 hours.

Spread lemon curd over chilled cheesecake. Refrigerate 1 hour.

Warm egg whites, sugar, and cream of tartar over a double boiler until sugar dissolves. Beat to stiff glossy peaks. Mix in vanilla and spread over cheesecake.

Torch or broil meringue until lightly golden. Refrigerate until serving.