Brush each filet generously with sesame oil so it is well coated on all sides. On a small plate, arrange your 2 tbsp coarsely grated peppercorns and 1 to 2 tsp salt (to taste) evenly. Dip each fillet into the peppercorns so that they form a thick crust on both sides. Add more peppercorns if need be to ensure the tuna is well crusted on both sides. Heat your grill to medium-high heat (about 400 degrees). Sear the tuna steaks on each side for no longer than 2 1/2 minutes. Serve with low-sodium soy sauce and wasabi. The tuna will be rare (sushi style) in the middle and seared on the outsides. If you do not like rare tuna, then cook the steaks longer on the grill to your desired doneness.