In a large bowl, add the tuna and avocado. Use a fork to smash the avocado and tuna together.
Add the carrots, celery, red onion, Dijon mustard, lemon juice, garlic powder, salt, and pepper. Stir to combine.
Lay a tortilla flat on a plate. Lay a lettuce leaf on the tortilla. Scoop ¼ of the tuna mixture into the center of the lettuce and spread down the middle. Top with cherry tomatoes and carefully roll the the tortilla to create a wrap. Repeat with the remaining ingredients.