Wash, pit, and dice the peaches, then combine them with sugar, water, and lemon juice in a saucepan. Heat over medium until simmering for 10-15 minutes.

Remove from heat and cool slightly. Mash the peaches, then strain through a sieve to make a smooth puree.

In a small saucepan, make a simple syrup by combining equal parts sugar and water over medium heat until dissolved.

Juice lemons and strain into a pitcher. Mix in the cooled simple syrup.

Combine the peach puree with the lemonade base, adding cold water to taste.

Chill the mixture in the refrigerator for at least 30 minutes, then serve over ice and garnish.