Tropical Cheesecake

1-1/2 c. graham cracker crumbs
6 tbsp. butter, melted
1/4 c. granulated sugar
9 inch spring-form pan
1-1/2 lbs. cream cheese
2 tsp. vanilla extract
4 egg whites
1 c. granulated sugar
1-1/2 tbsp. lemon, lime, or orange extract
Sour Cream Topping
2 c. sour cream
3 tbsp. granulated sugar
Crust: Preheat oven to 350 degrees. Place crumbs in mixing bowl and add butter and sugar; blend well. Press crumb mixture onto bottom and partially up sides of greased spring-form pan. Smooth crumb mixture along bottom to an even thickness. Bake 10 minutes; cool before filling.
Filling: Preheat oven to 350 degrees. In a large mixing bowl, beat cream cheese with vanilla until soft and fluffy. Stir in extract. Beat egg whites into the cream cheese mixture. Pour mixture into pie crust and bake for 25 minutes. Meanwhile, prepare Sour Cream Topping.

Topping: In a mixing bowl, stir together sour cream and sugar to blend. After cake has baked, remove from oven and turn up the temperature to 450 degrees. Spread the Sour Cream Topping over the top of the cake. Return cake to oven and bake at 450 degrees for about 5 minutes. Cool to room temperature, then chill.