On a baking sheet lined with aluminum foil, arrange slices of limes and clementines and sprinkle them with sugar and broil them just until sugar crystalizes and the slices are charred.
On a grill pan, char the lime halves until lightly charred.
In a shallow dish, combine salt and sugar. Moisten two cocktail glasses with a lime and rim the glasses with the salt-sugar mixture. Fill glasses with ice and set aside.
Muddle charred lime and jalapeño in a cocktail shaker.
Add tequila, orange liqueur, lime juice, and clementine juice and fill with ice. Shake cocktail shaker until frosted.
Strain drink into prepared glasses and garnish with broiled lime and clementine slices, if using.
Notes
As for the tequila, I recommend Exotico reposado. This tequila has hints of spices, with a finish of oak and pairs perfectly with all the smoky flavors in this cocktail.