1 (10-ounce) package frozen pitted sweet cherries (2 cups), thawed
1 cup freshly squeezed lemon juice
1 cup sugar
5 cups chilled seltzer water, plus more to taste
Add the cherries, lemon juice, and sugar to a blender and puree. Pour the mixture into a large pitcher. Add the seltzer and stir gently. Pour into glasses filled with ice and top with additional seltzer, if desired.