SERRANO SPICED PALOMA

1 ounce fresh lime juice (which is about 1 lime, juiced)
½ teaspoon light agave nectar or 1 teaspoon simple syrup
1 thinly sliced serrano round (⅛th to ¼th inch wide, a little goes a long way!)
2 ounces fresh grapefruit juice (which is less than 1 grapefruit worth of juice)
2 ounces silver or blanco tequila
1 ½ ounces grapefruit-flavored club soda or plain club soda
Salt rim and garnish
2 teaspoons kosher and/or sea salt
Lime wedge, for lining the rim
Small grapefruit wedges, for garnish