Cover a baking sheet with foil and arrange the four grapefruit halves in a single layer on top. Use a paring knife to cut in between the sections of each half, then trace around the edge. This will make the grapefruit pieces easy to remove and eat once the sugar is on top.
In a medium stainless steel pan, combine the sugar with 1/4 cup water, then swirl over medium heat to blend. Heat until it forms a clear syrup, 3 to 5 minutes. (Do not stir with any utensils.) When the sugar and the water have melted together completely, raise the heat gently and watch as the caramel darkens slightly to amber, 2 to 3 minutes more.
Pour the hot caramel over the tops of all the grapefruits halves and let cool, 3 to 5 minutes. The sugar should form a hard shell on top.
I really love the flavor of grapefruits and oranges. Some kinds more than others. I love a pink grapefruit. The simplest thing I like to do with grapefruits is split them, cut between the sections, sprinkle with some sugar and scoop it out and devour with an old-fashioned grapefruit spoon. You know, the funny one with the ridges on the end? I also love to cook them for a few minutes or coat them with a caramel, which makes a dessert for breakfast. Be careful when working with hot sugar. The sugar may melt a little unevenly in places, but once you start eating, it won't matter. The crunch. The sweetness. This is luxurious, with only 2 ingredients. Try sprinkling with a pinch of crunchy sea salt on top of the sugar, too….