Preheat oven to 350°F (175°C). Mix graham cracker crumbs, melted butter, and sugar in a bowl. Press the mixture into the bottom of a 9-inch springform pan. Bake for 10 minutes. Remove from oven and let cool.

Reduce oven temperature to 325°F (160°C). In a large bowl, beat the cream cheese, sugar, and flour until smooth. Add eggs one at a time, beating just until combined. Stir in vanilla extract, lemon zest, and lemon juice. Pour over the crust.

Bake for 55-60 minutes or until the center is set and the top appears dull. Remove from the oven and cool on a wire rack. Chill in the fridge for at least 4 hours or overnight.

While the cheesecake is cooling, whisk together lemon juice, lemon zest, sugar, and egg yolks in a saucepan over medium heat. Cook and stir until thickened and creamy. Remove from heat and stir in butter. Cool slightly, then spread over the chilled cheesecake. Refrigerate until well chilled.

When ready to serve, beat egg whites, sugar, and cream of tartar in a clean, dry bowl until stiff peaks form. Beat in vanilla extract.

Spread or pipe the meringue over the lemon curd layer. Use a kitchen torch to brown the meringue lightly, or place under a broiler for a few minutes, watching closely to avoid burning.

Serve immediately after adding the meringue topping, or keep refrigerated until ready to serve.