Preheat the oven to 325°F (160°C). Grease a 9-inch springform pan and line the bottom with parchment paper. Mix graham cracker crumbs, sugar, and melted butter in a bowl. Press into the pan and bake for 10 minutes. Let cool.

Beat cream cheese until smooth. Add sugar, lemon juice, and zest, and mix. Add sour cream and mix. Beat in eggs one at a time. Pour filling over the crust. Bake for 50-60 minutes until edges are set. Let cool in the oven with the door slightly open for 1 hour, then cool completely at room temperature before refrigerating for at least 4 hours.

For the lemon curd: In a saucepan, whisk butter, sugar, eggs, lemon juice, and zest over medium heat. Cook, stirring constantly, for 7-10 minutes until thickened. Strain to remove lumps and refrigerate.

For the meringue: Beat egg whites until frothy. Add cream of tartar and gradually beat in sugar until stiff peaks form. Spread lemon curd over the cheesecake, then top with meringue, spreading to the edges to seal.

Toast the meringue using a kitchen torch or broil for 1-2 minutes in the oven. Let cool, then refrigerate for 1-2 hours before serving.