2 slices fresh hot chili pepper, or 1 small pinch crushed red pepper (optional)
Arrange the fish steaks in a shallow ceramic or glass dish. Whisk together the lime juice, soy sauce, garlic, ginger, sesame oil, and chili pepper, if using, in a small bowl. Pour marinade over the fish and turn the fish to coat both sides with marinade. Cover with plastic wrap and let stand about 30 minutes at room temperature or 1 hour in the refrigerator, turning fish over once or twice and spooning marinade over the fish.
Heat the grill or broiler with the rack about 4inches from the heat source. Transfer the fish to a broiler pan spooning a little of marinade over the fish. Grill or broil, basting once or twice with marinade, until first side is nicely glazed and golden, about 5 minutes. Turn fish carefully with a wide spatula and spoon remaining marinade on top. Grill or broil second side, basting at least once with marinade left in the dish, just until fish is glazed but still pink inside, about 4 minutes. Do not overcook. Transfer fish to heated serving plates or a platter.