Rinse the fish and pat dry with paper towels. Slice into 1/2 inch steaks.
In a small bowl mix together the spices and set aside.
Place a frying pan or cast iron skillet over high heat until it starts to smoke. Keep kitchen area well ventilated.
Toss the ahi tuna in melted butter and then coat with spice mixture on both sides. Press spice mixture to adhere. Immediately sear on high heat each side for 10 seconds for pink in the middle, or for no more then 30 seconds per side to cook through well. Serve immediately.