Prepare grill by lighting 4 quarts of charcoal (1 starter chimney's worth), or turning gas grill to medium-high.
Examine steaks for pin bones by rubbing fingers over surface of meat. If found, remove with bone tweezers or pliers reserved for culinary uses.
Using a sharp paring or boning knife, trim bones from the cavity side of the steak. Trim the stomach flaps so that 1 side is missing about 2 inches of skin and the other, 1 inch of meat. Roll the skinless section up into the hollow of the cavity, then wrap the other around the outside to form a round resembling a filet mignon. Tie in place with 2 passes of butcher's twine. (Do not tie it too tight or fish will pop out during cooking.)
Combine cumin, coriander, fennel and peppercorns on a double thick piece of aluminum foil and toast over grill, shaking gently until seeds become fragrant. Crush seeds in mortar and pestle or pour into spare pepper grinder. Coat steaks lightly with oil, season with salt, then liberally grind toasted seeds on both sides of steaks.
Quickly wipe hot grill grate with a rag or towel dipped in a little Canola oil, then grill fish to medium rare, about 3 minutes per side. (Fish should be well colored on the outside and barely translucent at the center.
Serve steaks alongside simple salad dressed with "Veni, Vedi, Vinaigrette."