1. Light the grill or heat the broiler. In a small glass or stainless-steel bowl, mash the capers with a fork. Stir in the lemon juice, parsley, 1/2 teaspoon of the salt, and 1/4 teaspoon of the pepper and then 6 tablespoons of the oil.
2. Coat the tuna with the remaining 2 tablespoons oil. Sprinkle with the remaining 1/4 teaspoon each salt and pepper. Grill or broil the tuna for 4 minutes. Turn and cook until done to your taste, 3 to 4 minutes longer for medium rare. Serve the tuna topped with the sauce.
Variations: The lemon-and-caper sauce tastes great on almost any grilled fish. Swordfish or salmon steaks are especially good choices. Just adjust the cooking time according to the thickness of the fish.
Wine Recommendation: Though grilled tuna is superb with pinot noir, here the acidic sauce calls for a white wine. Gavi, Piedmont's cortese-based white, has just the right limelike accents to complement the tangy capers and lemon.