Mash avocado and then mix in remaining ingredients (tuna, pickle, celery, seasonings, mustard, mayo as needed.)
Place tortilla on a nonstick skillet (sprayed with cooking spray) and ⅓ of tuna mixture to tortilla and top with cheese (spread out evenly accross tuna mixture.)
Fold tortilla over on itself and cook on medium for 3-5 minutes on each side (or until each side is crispy and cheese is melted in the middle.)