Marinated Ahi Tuna

In a shallow non-aluminum bowl, combine the vinegar, onions, mustard and pepper. Whisk in the olive oil, a little at a time, until well incorporated. Coat the tuna with the marinade and marinate for 1-4 hours, refrigerated, turning occasionally.

Light a fire in a charcoal grill or preheat a broiler (griller). Remove the tuna from the refrigerator 30 minutes before cooking. Broil or grill the tuna 4-6" (10-15cm) from the broiler or very hot coals, 4-5 minutes per side for rare to medium rare doneness. Serve immediately with pineapple salsa.