Dip each filet into the coconut oil so it is well coated on all sides.
On a plate, arrange your coarsely ground peppercorns, sesame seeds and salt evenly. Dip each filet into the mixture 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.
Add sliced avocado and lemon wedges when platting