2 Tuna Steaks (about 1/4 lb. Each)
1 T. Soy Sauce
1 T. Rice Vinegar
1/8 tsp. Ground Ginger
1 T. Whipped and softened butter, divided
1/2 tsp. Dry Mustard

In non-reactive dish large enough for tuna in single layer arrange tuna. Combine soy sauce, vinegar and ginger and pour over tuna. Let stand five minutes, turn tuna over and let stand five minutes longer. Combine 2 tsp. butter and mustard, refrigerate until serving. In skillet melt remaining butter. Add tuna, reserving marinade and cook over medium-high heat until bottom of tuna is browned, about two minutes. Turn tuna over, drizzle with reserved marinade and cook another 2-3 minutes. Transfer tuna to plates, and top each with half the mustard butter.