Preheat oven to 325°. Place a greased 9-in. springform pan on a double thickness of heavy-duty foil (about 18 in. square). Wrap securely around pan.
In a small bowl, mix crushed wafers and melted butter. Press onto the bottom and 3/4 in. up sides of prepared pan. Bake 8 minutes. Cool on a wire rack.
In a large bowl, beat cream cheese, sour cream and sugar until smooth. Beat in lemon zest and juice. Add eggs; beat on low speed just until blended. Pour into crust. Place springform pan in a larger baking pan; add 1 in. of hot water to larger pan.
Bake until center is just set and top appears dull, 1 to 1-1/4 hours. Remove springform pan from water bath. Cool cheesecake on a wire rack 10 minutes. Loosen sides from pan with a knife; remove foil. Cool 1 hour longer.
Meanwhile, in a small heavy saucepan, whisk together first five curd ingredients. Add butter; cook over medium heat, whisking constantly, until mixture is just thick enough to coat a metal spoon and a thermometer reads at least 170°. Do not allow to boil. Remove immediately to a small bowl; cool completely.
Gently spread curd over cheesecake. Refrigerate overnight, covering when completely cooled. Remove rim from pan. If desired, top with fresh lemon zest strips.