1 cup sugar
4-6 lemons, preferably organic (because you'll use the zest)
A pinch of coarse salt
1. Find a pitcher that will hold 2 1/2 quarts of liquid. (If you don't have a large enough pitcher, you can either scale the ingredients down accordingly, or mix the ingredients in a large bowl and store the extra lemonade in the fridge until you have more room in your pitcher.)
2. Make lemony simple syrup: Put the sugar in a medium saucepan. Use a microplane or zester to zest one lemon and add the zest to the sugar (reserving the lemon). Add one cup of cold water and stir to combine. Heat the mixture over medium-low, stirring occasionally, until the sugar has melted. Turn the heat to low, put the lid askew and steep for 15 minutes.
3. Allow the syrup to cool to room temperature. (If you're in a hurry, you can speed this process by cooling it in an ice water bath like this: Choose a medium bowl that will fit inside a larger bowl. Put ice water in the bottom of the larger bowl. Pour the syrup into the medium bowl and set the bowl of syrup inside the larger bowl so that the ice water comes partially up the sides. Adjust the amount of ice water to be sure no water will get into the sugar syrup. In about 10-15 minutes, the syrup should be cool enough to work with.)
4. Squeeze the juice from the lemons to make 1 cup and add it to the pitcher. (Depending on the size of your lemons, you may not need all of them.)
5. Add the sugar syrup to the lemon juice. (You can choose whether to to strain the zest out of the syrup before adding it, or just leave it in. We usually leave it in; it's tender and sweet after its tour in the syrup and adds a bit of color and rustic texture to the lemonade.) Add 2 quarts of cold water to the pitcher along with a very small pinch of salt. Stir to combine.
6. Serve with ice in the glasses rather than the pitcher (so the ice doesn't dilute the lemonade as it sits).
You can make the lemony simple syrup ahead of time and store it covered in the refrigerator for several days. You can also freeze it in a covered container for months.
To prep several pitchers ahead of time for a party, combine several batches of lemon juice, lemony syrup and pinch of salt in covered containers - each container holding enough for one pitcher. Then at party time, simply pour the contents of each container into a pitcher and fill with water. Give it a quick taste and add more syrup if needed, and you're ready to go.