1. Preheat your oven to 350°F. Bring all cheesecake ingredients to room temperature.
2. Crush graham crackers and mix with melted butter. Line a 9-inch springform pan with parchment paper, firmly pressing the crust into the bottom and slightly up the sides. Bake for 8-10 minutes, then let it cool.
3. Lower the oven temperature to 325°F.
4. Wrap the pan with two large sheets of aluminum foil to prevent water leaks during the water bath.
5. In a stand mixer, beat the cream cheese, sugar, vanilla, and salt on medium speed until smooth. Add eggs one at a time on low speed, then mix in heavy cream, sour cream, cornstarch, and lemon juice.
6. Pour the cheesecake batter over the crust, tap the pan to remove air bubbles. Place in a water bath and bake for about 80 minutes, until the edges are firm and the center remains jiggly.
7. Allow to cool to room temperature for 2 hours then refrigerate overnight.
8. For the lemon curd, mix lemon juice, eggs, sugar, cornstarch, and salt in a saucepan. Cook on low, stirring constantly until thickened. Stir in butter, strain, and chill.
9. To make the Swiss meringue, whisk egg whites, sugar, and cream of tartar over simmering water until 150°F, then beat until stiff peaks form.
10. Spread the chilled lemon curd over the cheesecake. Top with meringue and toast using a kitchen torch until golden brown.