1/2 t lemon zestPlace zest and syrup (sugar to water, 1:1) in a 16 oz glass. Let mull for a minute while crushing with a teaspoon. Add lemon juice, ice, and sufficient water to top up the glass. Stir vigorously to chill.
1 oz freshly-squeezed lemon juice
2 oz simple syrup
water as needed
10 ice cubes
Serves one.