Crust: Combine all ingredients, press into 9" pie plate and bake at 350 F for 10 minutes. Cool.
Filling: Combine cheese, egg substitute, sugar, vanilla yogurt, lemon peel and juice, and vanilla extract in mixing bowl. Beat at low speed with an electric mixer until blended, and then increase speed and blend until smooth.
In small bowl, beat egg whites with cream of tartar until stiff but not dry. Gently fold egg white mixture into cheese mixture. Turn into the graham cracker crumb crust and bake at 325 F for 35 minutes or until set. Remove from the oven and cool on a wire rack. Spread lemon topping over the pie. Chill at least 12 hours or overnight before serving.