1 1/2cupsfresh lemon juice(8-12 lemons, depending on size and juiciness)
1Tablespoongrated lemon zest
In a medium size saucepan over high heat, bring sugar and 2 cups water to a boil, stirring until the sugar has dissolved. Boil, uncovered, for 5 minutes. Stir in the lemon juice and zest. Remove the pan from the heat, cover, and let stand for 30 minutes.
Strain through a sieve into a 2 quart pitcher, then stir in the remaining 1 cup water. Cover with plastic wrap and chill 2 hours or overnight. To serve, fill the pitcher or a tall glass with ice cubes and fresh lemon slices.