I added hot water to dissolve the sugar, making a lemon-infused simple syrup of sorts, and juiced the zested lemons plus three more. Knowing that heat dampens the brightness and complexity of citrus juice, I waited until the syrup had cooled completely before stirring in the lemon juice. I strained out the zest, mixed in an equal amount of cold water, poured it over ice, and was rewarded with my best batch yet: bracingly sour and sweet, with bitterness that was just a smidge over the line. (When zest meets juice, some of the same reactions that cause bitterness happen.) But it was an easy fix: I added a dash of salt—a trick we often use to mask bitterness and enhance other flavors in foods such as eggplant and coffee—to dull its harsh edge, leaving the lemonade perfectly balanced.