I love Halibut, and now I grill it -whether steak or filet.
I don't put sauce on, maybe squeeze a lemon over the top & tiny pinch of salt.
However, I had monkfish w/ grapefruit sauce at at local restuarant a couple of months back & it blew me away. It wasn't smothered in it & hardly enough to sop up w/ the rice. I've been intrigued w/ it ever since. I've found some recipes online for sauce but nothing seems to fit what I had w/ the monkfish.
If anyone has an idea with Grapefruit I would certainly welcome it.