Combine paprika, oregano, garlic pwdr, onion pwdr, salt, cumin, pepper, and cayenne pepper on a plate. Brush oil over tuna steaks. Press tuna steaks into spice mix; gently rub spices onto one side of the fish.
Grill 'em up! About 3-4 minutes on the blackened side, and half that on the other. You can also pan-sear this, but you'll want to get the pan nice and hot.