Preheat your oven to 325°F (163°C). Lightly grease a 9-inch springform pan.

In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted unsalted butter. Mix thoroughly and press into the bottom of the prepared pan. Bake for 10 minutes and cool completely.

Beat cream cheese until smooth, then gradually add sugar, stirring in sour cream, eggs one at a time, vanilla, zest, and lemon juice until smooth.

In another bowl, whisk together heavy cream, cornstarch, and salt. Fold into cream cheese mixture. Pour over cooled crust and bake for 55-60 minutes until slightly jiggly.

Turn off the oven and cool the cheesecake inside for 1 hour with the door ajar. Refrigerate for at least 4 hours or overnight.

Beat egg whites and cream of tartar until soft peaks form. Gradually add sugar until stiff peaks form. Mix in lemon juice and vanilla.

Spread meringue over cheesecake, creating peaks and swirls. Increase oven temperature to 350°F (177°C) and bake for 8-10 minutes until golden brown.

Cool at room temperature for 15 minutes, then refrigerate for at least 1 hour before serving.