Prep the tamarind juice up to one day ahead for an easy cocktail.
In a saucepan, bring the water and sugar to a boil over high heat.
After the water comes to a boil and the sugar has dissolved, pour the boiling water over the tamarind in a mixing bowl. Allow the hot water to loosen up the pulp.
Chill the liquid in the refrigerator for one hour (or until very cold).
Combine the Tajín, kosher (or sea) salt, and a couple drops of liquid smoke in a shallow bowl or dish. Use a spoon or your fingers to incorporate the liquid smoke into the spices.
Cut one of the lime halves into wedges. Rub one wedge, per glass, around the rim of your old-fashioned glass to moisten it. Reserve the remaining lime for adding to the cocktail.
Dip the wet rim into your smoked salt mixture to coat it well. Set the glasses aside to dry while you prepare the margarita.
Fill a cocktail shaker with a handful of ice. Pour the añejo, triple sec, the lime juice from the leftover limes, and a cup of the chilled tamarind juice. Store the remaining tamarind juice in the fridge.
Cap the shaker and shake vigorously until the shaker frosts over.
Strain the margarita into your ice-filled, salt-rimmed margarita glasses. Sprinkle a bit more of that smokey salt over the margarita, if desired.
Serve immediately. Enjoy responsibly.
To make pitcher margaritas, just quadruple the recipe.
For a kid-friendly drink, omit the añejo and triple sec and serve over ice.