Preparation / Directions:
Season fish with salt and pepper. Melt 1 tablespoon butter in heavy medium skillet over medium heat. Add fish and cook until just opaque, about 9 minutes per inch of thickness, turning once. Transfer fish to warm platter. Tent with foil to keep warm.
Pour off all but film of butter from skillet. Add shallots and rosemary and stir over medium heat until shallots soften, about 2 minutes. Add grapefruit juice. Increase heat and bring to boil, scraping up any browned bits. Add any juices from the fish platter.
Boil until sauce is syrupy, 5 to 8 minutes. Remove from heat and swirl in 2 tablespoon butter, 1 tablespoon at a time. Season sauce with salt and pepper. Spoon over fish. Garnish with parsley.