Preheat oven to 325°.
To prepare crust, combine first 4 ingredients in a bowl; toss with a fork until moist. Press into a 9-inch pie plate coated with cooking spray. Bake at 325° for 15 minutes or until lightly browned; cool on a wire rack.
To prepare filling, combine lemon rind and next 3 ingredients (rind through yogurt) in a medium bowl, and set aside. Sprinkle gelatin over 3 tablespoons water in a small microwave-safe bowl; let stand 1 minute. Microwave at HIGH 15 seconds, stirring until gelatin dissolves. Stir gelatin mixture thoroughly into yogurt mixture. Spoon filling into prepared crust. Press plastic wrap onto surface of filling; chill 1 hour or until almost firm.
To prepare the meringue, combine 2/3 cup sugar and 1/4 cup water in a small saucepan; bring to a boil. Cook, without stirring, until candy thermometer registers 240°. Beat egg whites and cream of tartar at high speed of a mixer until foamy. Pour hot sugar syrup in a thin stream over egg white mixture, beating at high speed until stiff peaks form. Remove the plastic wrap from filling. Spread meringue evenly over filling, sealing to edge of crust.
Broil meringue for 1 minute or until lightly browned, and cool on wire rack. Chill until set.