Look for large, slightly soft lemons—they tend to be extra-juicy. Store the lemonade in a covered container in the refrigerator for up to 3 days.
1 large lemon ,
sliced thin, ends discarded
1 1/2 cups sugar
7 cups cold water
2 cups fresh lemon juice (from about 12 lemons)
Ice (for serving)
Using potato masher, mash lemon slices and sugar in deep bowl until slices release their juice and sugar begins to dissolve. Stir in water and lemon juice until sugar completely dissolves. Strain out lemon slices and chill or pour over ice before serving.