Preheat broiler. To section grapefruit, cut out core, then cut along the sides of the "shell" and remove fruit, keeping skin intact. Remove membranes. Saute grapefruit sections and peppers in clarified butter on medium heat. Add lemon and crabmeat. Reduce heat to low.
Spoon saute mixture into grapefruit shells. Spoon mayonnaise on top. Cross 2 pimentos on top of mayonnaise. Broil for 4 minutes.