1 1/2 cups freshly squeezed lime juice (from about 15 limes), plus slices for garnish
1 cup tequila blanco, or to taste
1/2 cup Cointreau
1/2 cup simple syrup, or to taste (see Cook's note)
Coarse salt, for rimming
1 750-ml bottle prosecco, chilled
To make simple syrup, simmer equal parts sugar and water until the sugar is dissolved, then let cool.