Preheat broiler. Mix the Bourbon (1 teaspoon), Brown Sugar (2 teaspoon), and Ground Cinnamon (1/8 teaspoon) together in a small bowl, and then set aside.
Cut around the edge of the Grapefruit (1/2) to loosen the fruit.
Spread the sugar mixture over the top of the grapefruit, and then place in the broiler for about 10 minutes. Cook until the fruit is slightly bubbling, but not burnt.
Remove, and serve immediately with a grapefruit spoon. Enjoy!