Preheat oven to 325°F (165°C). Grease a 9-inch springform pan. Combine shortbread crumbs and melted butter, then press firmly into the bottom of the pan.
Beat cream cheese, sour cream, and sugar until smooth. Add eggs one at a time, mixing gently. Mix in lemon juice, lemon zest, and vanilla until just combined.
Pour filling over crust and smooth the top. Bake for about 60 minutes, until edges are set and the center slightly jiggles. Cool at room temperature for 1 hour, then refrigerate at least 3 hours.
Increase oven temperature to 375°F (190°C). Beat egg whites until soft peaks form. Gradually add sugar and cream of tartar, beating until stiff, glossy peaks form.
Spread lemon curd evenly over the chilled cheesecake. Top with meringue, sealing completely to the edges. Bake 8–10 minutes until lightly golden. Chill uncovered at least 1 hour before serving.
