In a small saucepan over medium-low heat, whisk together lemon zest, juice, sugar and eggs. Stir in butter and cook, stirring constantly, until curd thickens, about 5 minutes. Strain through fine mesh sieve and refrigerate, stirring occasionally, until completely cooled.

Preheat oven to 350 degrees F. Stir together graham cracker crumbs, sugar, salt, and melted butter. Press into a 9-inch springform pan. Bake for 10 minutes; cool on wire rack.

Reduce oven temperature to 300 degrees F. In the large bowl of a standing mixer, beat together cream cheese and sugar until light and fluffy. Reduce speed to low and beat in eggs, one at a time, until incorporated. Beat in sour cream and vanilla.

Pour two-thirds of the cheesecake batter into the crust, and top with half of the lemon curd. Swirl gently with a knife. Top with remaining cheesecake batter and lemon curd, and repeat swirling. Bake in centre of oven for 45-55 minutes, until set (centre may still jiggle a bit, it will firm up). Cool completely before serving.