Early in the day:
1. In a medium bowl, combine flour, 6 tablespoons sugar, and 1 teaspoon grated lemon peel.
With pastry blender or two knives used scissor fashion, cut in butter or margarine until mixture resembles coarse crumbs. With a fork, stir in 2 egg yolks and half teaspoon vanilla to form a very stiff dough. Chill 30 minutes. Preheat oven to 425 degrees, F.
2. Press one third of the chilled dough evenly into the bottom of a 23 cm springform pan. Bake 8 10 minutes until golden brown. Cool. Press rest of dough around sides of pan to within 3 cm of top. Do not bake.
3. In a large bowl, with mixer at high speed, beat cream cheese until smooth' gradually add Cheddar cheese, beating until well blended about 5 minutes.
Occasionally scrape bowl with rubber spatula.
4. At medium speed, gradually beat in half teaspoon grated lemon peel, half teaspoon vanilla, 1.75 cups sugar, 2 egg yolks, and remaining ingredients until blended.
Beat 5 minutes, occasionally scraping bowl.
5. Pour mixture into crust. Bake 10 minutes. Turn oven control to 150ºC and bake 1 hour and 15 minutes longer or until top is firm when lightly pressed with a finger.
6.
Cool in pan on wire rack. Cake will sink in center, leaving cracks around crust. With spatula, loosen pan side and remove. Loosen cake from pan bottom; slide onto plate; chill. Makes about dozen servings.