Heat a grill pan to medium high heat and brush with canola oil. Add quartered grapefruit, flesh side down, and grill until well charred, 2–3 minutes per cut side. Remove from grill and allow to cool.

Juice grapefruit, straining seeds and reserving one juiced wedge. In a cocktail shaker, muddle together charred grapefruit juice and cilantro. Add Sweet Tea (and alcohol, if using) and plenty of ice and shake until well chilled.

Rub the rim of two rocks glasses with the reserved grapefruit wedge. Spread the smoked salt on a plate and swirl the rims of each glass through the salt to coat. Add ice to glasses.

Strain the grapefruit/tea mixture into the glasses. Garnish each with a few cilantro leaves and serve immediately.