Directions

1. Make the syrup  Put the sugar and water into a heavy saucepan set over medium-high heat. Stir very gently to mix the sugar and water. Heat until the sugar has dissolved, then add the pepper, celery, parsley, ajwain, and a pinch of salt. Continue to heat until boiling; boil for 1 minute. Remove the pan from the heat and set aside to infuse and cool to room temperature, 20-30 minutes. Pour the syrup through a fine mesh strainer into a clean jar and discard the solids. Cap the jar and store in the fridge.
2. Make the herbed sugar for the rims  Put the pepper into a mortar and pestle (or clean coffee grinder) and grind until it’s the texture of coarse sand. Add the sugar and tarragon and grind to a fine powder. Store in a tightly sealed container.
3. Make the limeade  Set out a large pitcher (one batch is just over a quart, plus you’ll need room for ice). Set out 4 Collins glasses.
4. Pour the herbed sugar into a small, shallow bowl that’s wider than the diameter of the glasses. Moisten the rim of each glass (a small piece of lime works well). Dip the rim of each glass into the bowl of sugar and set the glasses aside.
5. Put the mint and celery leaves into the pitcher and use a spoon to bruise them slightly. Add the lime slices, followed by the lime juice, syrup, and a pinch of salt. Stir to mix, then stir in 1 can of seltzer. Add 2 cups ice and the remaining 2 cans of seltzer, give a gentle stir. Pour into the rimmed glasses and serve.