Position an oven rack about 4–6 inches below the broiler and turn the broiler on to preheat.
Drain 5 ounces chunk light tuna in water and place in a medium bowl; flake with a fork.
Add 1/4 cup Greek yogurt (low-fat, plain) or the 1/4 cup mayo option from the ingredient list, then add 1/4 teaspoon kosher or sea salt and 1/4 teaspoon black pepper. Stir until evenly combined.
Spread the tuna mixture in a broiler-safe baking dish or pan in an even layer. Sprinkle 1/2 cup shredded reduced-fat cheddar cheese evenly over the top.
Place the dish under the preheated broiler for about 1–2 minutes, watching closely, just until the cheese melts and begins to bubble. Remove from oven.
Lay the large whole-wheat wrap flat on a clean work surface. Arrange the 4 butter lettuce leaves (or large iceberg leaves) down the center of the wrap.
Scoop the tuna with melted cheese onto the lettuce, leaving a 1–2 inch space at one short end. Top with the 4 pickle slices or jalapeño slices, if using.
Tuck the short end of the wrap under the filling and roll tightly to enclose. Cut the wrap in half and serve.