- In a bowl, combine the soy sauce and harissa sauce. Add the tuna and coat thoroughly with the marinade. Let rest for about 15 minutes, or longer, in the refrigerator.
- Preheat the grill, setting the burners on high. Oil the grate.
- Drain the tuna and coat with the sesame seeds. Grill for about 1 1/2 minutes per side or until the desired doneness. Season with salt and pepper.