Grilled Marinated Salmon with Rio Star Grapefruit Beurre Blanc

Peel, section and chop grapefruit. Set aside.
In a small bowl, whisk miso, mirin and rice vinegar. Place filets in a 9 x 13-inch baking pan. Pour marinade over fish and turn to coat. Cover and chill 30 minutes or up to 2 hours.
In a small saucepan over medium heat, simmer grapefruit juice, wine, shallot and white wine vinegar. Simmer until reduced to about 1 tablespoon. Reduce heat to low and whisk in butter one piece at a time, adding each new piece of butter just before previous piece has completely melted. Avoid overheating sauce to prevent separation. Stir in chopped grapefruit and season with salt and pepper. Pour sauce into a metal bowl set over a saucepan of hot water, being careful not to allow bottom of bowl to come in contact with hot water.
Brush grill with vegetable oil and heat to low-medium heat.
Transfer marinade to a small saucepan and heat to boiling. Brush each salmon filet with 1 tablespoon of marinade and grill three minutes. Turn and brush with marinade. Grill until salmon is cooked through, about 5 minutes, being careful not to overcook.
To serve, place salmon on individual plates and spoon sauce around filets. Garnish with grapefruit zest.