Crust:
1 cup flour
¼ cup sugar
1 teaspoon finely grated lemon zest
1/8 teaspoon salt
1 stick unsalted butter, cut into ½ inch pieces and chilled
Filling:
1 tablespoon plus 2 teaspoons cornstarch
½ cup cold water
2 large egg yolks
1 ¾ cups sugar
¼ cup fresh lemon juice
1 teaspoon grated lemon zest, chopped
1 ¼ pounds cream cheese, softened
2 tablespoons flour
3 eggs , room temperature
¼ cup sour cream
1 teaspoon vanilla
Make Crust: Preheat oven to 325. Butter a nonstick 9-inch baking pan. In a food processor, pulse flour with sugar, lemon zest and salt. Add butter and pulse until a soft, crumbly dough forms. Press dough evenly over bottom and a scant ½ inch up the side of pan. Bake crust for 20 minutes or until golden and firm.
Filling: In a small bowl, dissolve cornstarch in water. In medium sauce pan, whisk egg yolks with ¾ cup sugar and lemon juice. Whisk in the cornstarch mixture and cook over moderate heat, whisking gently until sugar is dissolved and lemon mixture is hot, about 4 minutes. Boil over moderate heat for 1 minute, whisking constantly, until the mixture is thick and glossy. Strain lemon mixture into a heatproof bowl. Stir in lemon zest and let cool.
In large electric mixer, beat cream cheese with remaining 1 cup of sugar until smooth. Beat in flour until blended; add eggs, one at a time, beating well between additions. Add sour cream and vanilla and beat until the batter is smooth. Pour cream cheese batter over crust and smooth the surface with a spatula. Dollop the lemon mixture on the cheese cake batter and carefully swirl it into the batter but do not cut into the crust.
Bake for about 40 minutes or until golden around the edge and just set. Run tip of knife around the edge to loosen cheesecake from the side of pant. Let cool for one hour, then refrigerate until thoroughly chilled. Cut into 16 bars. This can be refrigerated in the pan for up to three days.