Preheat your oven's broiler. Line a cookie sheet with aluminum foil.

Cut the grapefruit in half and use a small knife to loosen the flesh from the skin. Pour juices and sections of grapefruit into a bowl.

Scrape out the remaining pulp from the skins, creating little grapefruit bowls. Spoon the grapefruit and juices back into the grapefruit bowls. Sprinkle with cinnamon and sugar, and place small dots of butter across the surface of each grapfruit bowl.

Place the bowls on the cookie sheet and broil for 3-5 minutes, until the butter is melted and the sugar is starting to brown. Allow to cool for a minute or two before serving. Enjoy!