Chill grapefruit. Line a baking sheet with foil.
Cut and segment grapefruit. Slice a small piece off of bottom rind so that each half sits flat on baking sheet.
Sprinkle a tablespoon raw sugar or light brown sugar onto cut and segmented grapefruit.
Broil on high for 5 min, and top with whipped cream and sprinkle of cinnamon.