Just a few minutes under the broiler caramelizes the brown sugar which is a perfect compliment to the tart flavor of the grapefruit. From the book "Mad Hungry" by Lucinda Scala Quinn. (Artisan Books).
Mad Hungry, November 2010 http://www.marthastewart.com/349783/broiled-grapefruit-halves-topped-brown-sugar© 2013 Martha Stewart Living Omnimedia. All rights reserved.