To prepare crust, combine flour, sugar, and lemon peel. Cut in butter until crumbly, and then add egg and vanilla. Pat just enough into the bottom of a 9" springform pan (with sides removed) to cover. Bake in a 400 degree oven for 7 minutes or until golden; cool.
Butter the sides of the pan and attach to bottom. Pat remaining dough onto the sides of the pan to a height of 1 3/4" and set aside. Note: you may have extra dough left, and if so discard. I doubled the crust recipe because I found the original did not make enough.
For the filling, in a large mixer bowl beat the cream cheese, lemon peel, and vanilla until fluffy. Stir together the sugar, flour and salt and then gradually stir into the cream cheese mixture. Add eggs and egg yolk all at once, beating at low speed until just combined. Stir in mulk, and pour into crust-lined pan.
Bake in a 450 degree oven for 10 minutes, then reduce heat to 300 and bake for 50-55 minutes more or until toothpick inserted in center comes out clean. Cool 15 minutes, then loosen sides of cheesecake from pan with a spatula. Cool another 30 minutes and then remove sides of pan. Cool about 2 hours longer, then chill thoroughly before topping with pie filling.