On 4 large sheets of aluminum foil, evenly distribute the tuna, cabbage and onion.
In a small bowl, mix together the next 8 ingredients (salt and pepper through honey). Spoon half the sauce over the tuna and vegetables and set the remaining sauce aside.
Lay a second sheet of aluminum foil on top of the tuna mixture and fold the seams to seal the pouches. Place pouches on the grill and grill on each side for 5 to 10 minutes, until tuna reaches desired level of doneness and vegetables are tender.
On collard leaves, spoon the tuna mixture. Drizzle the remaining sauce over the tuna mixture, wrap up leaves and serve.