Halve the grapefruit crosswise. Using a paring knife, cut between sections of the grapefruit so it is easier to eat once caramelized. Pat the surface dry with a paper towel.
Sprinkle the coconut sugar in an even layer on each grapefruit half. Place one grapefruit half sugar-side up on the bottom of an overturned bowl.
Preheat a nonstick skillet over high heat. (Do not add oil to the skillet.) Once the skillet starts to smoke, turn off the heat and place the hot skillet, nonstick-side down, on the sugared part of the grapefruit half on the bowl. Allow the skillet to stop sizzling before removing the skillet, about 1 minute. Repeat the process with the second grapefruit half.
Remove the skillet and allow the grapefruit to cool slightly.