Two of Martha's young friends, Arianna and Ivan, learn how to make healthy tuna and cheese roll-ups.
In a medium bowl, toss the apples with the lemon juice until coated. Add the tuna, celery, mayonnaise, salt, and pepper and stir with a fork until tuna is broken up and mixture is combined.
Lay the lavash on a large sheet of parchment paper on a work surface and cover with the cheese slices in a single layer, followed by a single layer of lettuce leaves. Evenly place the tuna salad along the bottom edge of the lavash. Using the parchment as a guide, tightly roll the sandwich beginning with a long side and wrap tightly in the parchment, taping the paper as necessary.