Step 1

If you like salt on your rim, add a few tablespoons to a wide, shallow bowl. Zest half the grapefruit into the bowl and stir to combine. This will make enough to salt several cocktails and you can save the leftovers in a Ziploc for a day or two.

Step 2

Chop the jalapeno (leave the seeds and pith to make it a little spicier; remove them for milder) and add them to a cocktail shaker or sturdy glass along with the agave syrup. Use a muddler or the handle of a wooden spoon to muddle the jalapenos (basically, gently mash to release the flavor and start infusing the syrup), then add the grapefruit and lime juices. For a spicier drink, let it infuse for at least 15 minutes.

Step 3

If you're salting your glass, use a paring knife to cut a small slit into the grapefruit wedge and rub it along the rim to moisten it, then roll it in the salt until coated. Gently tap away any excess.

Step 4

Fill the glass with ice and pour in the cocktail, jalapenos and all. Top with sparkling water, 1/3 to 1/2 cup or to taste. Serve with the grapefruit wedge.