Preheat the oven to 400 degrees F (200 degrees C). Place the whole pita breads in a single layer on a baking sheet. Bake for 5 minutes, or until lightly toasted.
In a medium bowl, mix together the tuna, mayonnaise, relish, dill and salt. Spread an equal amount of the tuna mixture onto each of the pita breads. Arrange tomato wedges over the tuna, and sprinkle with shredded Cheddar cheese.
Bake for 5 minutes in the preheated oven, or until cheese has melted.