Add all the ingredients into shaker with ice, and shake until well-chilled.
Strain into a Collins glass or Tiki mug over crushed ice.
Cut a lime in half, squeeze out the juice of one half, set atop the drink, pour overproof rum inside the shell, and carefully light on fire.
*Cinnamon-cumin syrup: Toast 1 tbsp cumin seeds in a sauté pan on medium-low heat until fragrant. Let cool, then grind into a coarse powder. Bring 2 cinnamon sticks and 1 cup water to a boil in a medium-size saucepan, and allow to boil for 10 minutes. Turn off the heat, add 2 cups granulated sugar and the toasted cumin powder, and stir until sugar has dissolved. Allow the syrup to cool, then strain through a fine-mesh strainer. Bottle and refrigerator for up to 2 weeks.