10cupscubed watermelon(about ½ medium watermelon; see Note)
1cupfresh lemon juice
Ice (to serve)
Instructions
Make the simple syrup: Place the water, sugar, and salt in a small saucepan over medium heat and bring to a simmer. Stir occasionally until the sugar dissolves, about 5 minutes. Cool the simple syrup to room temperature, then chill the syrup.
In a food processor or a blender, puree the watermelon in batches until completely smooth. Strain through a fine-mesh sieve. Discard the solids. You should have about 5 cups of juice.
In a pitcher, combine half of the simple syrup, watermelon juice, and lemon juice. Chill for at least 2 hours, until very cold. Stir the watermelon lemonade and serve over lots of ice in glasses.
Notes
Frozen Watermelon Lemonade Slushie: If you want to make a frozen watermelon lemonade slushie, freeze the watermelon cubes before putting them into the food processor. And skip the ice. No need to strain out the solids; just puree with the lemon juice and simple syrup until slushy and well blended.