01 - In a blender, combine the lemon juice, lemon zest, sugar, milk, vanilla extract, and ice cubes. Blend until smooth and frothy.
02 - In a clean, dry bowl, beat the egg white with cream of tartar until soft peaks form. Gradually add sugar while continuing to beat until glossy, stiff peaks form.
03 - Pour the blended lemon mixture into two tall glasses. Spoon or pipe the meringue on top of each drink.
04 - Garnish with additional lemon zest and a sprinkle of crushed graham crackers if desired. Serve immediately with a straw and a spoon.