Cut grapefruit in half and place in an oven/broil-safe dish.
Sprinkle brown sugar and cinnamon to your liking.
Take a picture of grapefruit bathed in sunlight while leaving a floury thumbprint on the tablecloth.
Place grapefruit within several inches of broiler at the top of the oven.
Broil on high for ~8-10 minutes (Broiling time may vary depending on the oven; mine seems to take longer).
Serve with a generous dollop of plain yogurt.
So simple. So tasty. So good for you!