2 cups watermelon puree (from about 1/4 large melon or 1/2 small melon)
1 cup freshly squeezed lemon juice (from about 5 heavy lemons)*
3/4 cup simple syrup
3 cups cold water
Ice, for serving
First, make the simple syrup. Heat 1 cup cold water with 1 cup sugar in a small saucepan over medium-high heat, stirring until sugar is completely dissolved. Remove from heat to cool.
Next, make the puree. Place large chunks of watermelon in food processor (blender would work too) and pulse until liquidy. Strain through fine sieve into medium-large bowl to remove seeds.
Juice lemons and measure out 1 cup. Pour through sieve to remove seeds.
In large pitcher, combine lemon juice, watermelon puree, 3/4 cup simple syrup (or more or less to suit your taste), and cold water; stir to combine. Serve in glasses filled with ice.
Chill remaining lemonade, stirring before serving (puree will separate out).
*The heavier the lemon, the more juice it contains. Always try to juice room temperature lemons, they'll give up more juice.
adapted from Smitten Kitchen