1. Place the tuna in a bowl to fit. Add the oil, lemon juice, salt and pepper. Turn the tuna to coat well in the marinade. Let rest 15 to 20 minutes, turning once.
2. Place the peppercorns in a double thickness of plastic bags. Tap the peppercorns with a heavy saucepan or small mallet to crush them coarsely. Place on a large plate.
3. When ready to cook the tuna, dip the edges into the crushed peppercorns. Heat a nonstick skillet over medium heat. Sear the tuna steaks, in batches if necessary, for 4 minutes per side for medium-rare fish, adding 2 to 3 tablespoons of the marinade to the skillet if necessary to prevent sticking. Serve dolloped with Roasted Orange Garlic Mayonnaise (optional).
Serves 6. Per serving: 280 calories, no carbohydrate, 51g protein, 7g fat, 100mg cholesterol.
Next up: Bobby Flay's Tuna Nicoise Sandwiches