Zest a lemon and set aside the zest. Then peel the lemons and remove any seeds. Discard peels and seeds. 2 medium lemons
Add the lemons, zest, sugar, ice and water to a blender and pulse until it is blended to the consistency you'd like. Zest of 1 lemon, 1/3 to 1/2 cup granulated sugar, 3 cups ice cubes, 1 1/2 cups cold water
Blend longer for a smoother frozen drink, and blend less for a icier drink.
Notes
Sweetness: Start with 1/3 cup sugar for tart, 1/2 cup for sweet, then adjust to taste after blending.
Texture: more ice thickens it, more water thins it.
Serve within 15 minutes for the best frosty texture. It does not refreeze well so blend right before serving.
Make it creamy: blend in a scoop of vanilla ice cream for a frosted, Chick-fil-A style version.