For crust, in a medium bowl, beat 2/3 cup butter with an electric mixer on medium speed for 30 seconds. Add 1/2 cup sugar and 1 teaspoon lemon peel; beat until combined. Beat in flour until crumbly. Press into the bottom of an ungreased 13x9x2-inch baking pan. Bake in a 350 degree F oven for 15 to 18 minutes or until edges are lightly golden. Remove from oven; set aside.
In a medium skillet, melt the 3 tablespoons butter. Add cornflakes and the 1 teaspoon sugar. Cook and stir over medium heat for 1 to 2 minutes or until cornflakes are lightly browned. Remove from heat; set aside.
In a medium bowl, beat eggs until foamy. Add the 1/4 cup sugar; beat until thick and lemon colored (about 5 minutes). Fold in sour cream and the 1/2 teaspoon lemon peel.
In a large saucepan, bring the apples and a small amount of water to boiling; reduce heat. Cover and simmer for 3 minutes or until apples are just tender. Drain well. Cool slightly.
In a small bowl, combine 1/2 cup sugar, the cinnamon, and 1 teaspoon lemon peel. Toss with the apple slices. Arrange coated slices over baked crust. Pour sour cream mixture evenly over apples. Sprinkle with cornflake mixture.
Bake in the 350 degree F oven about 35 minutes or until apples are tender and topping is golden brown. Cool slightly. Cut into squares. Makes 12 servings.