In a medium bowl, combine the drained tuna, mayonnaise, Dijon mustard, celery, red onion, lemon juice, salt, and pepper. Mix until well combined.
Lay out the flour tortillas on a clean surface.
Spread an even layer of the tuna mixture onto each tortilla, leaving about an inch of space around the edges.
Top the tuna mixture with shredded lettuce, cherry tomatoes, and cheese if using.
Carefully roll each tortilla tightly, starting from one end and tucking in the sides as you go.
Slice the wraps in half diagonally and serve immediately, or wrap in plastic wrap and refrigerate for up to 2 hours before serving.