Preheat the oven to 200 degrees C. Place the whole pita breads in a single layer on a baking tray. 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 grated Cheddar cheese.
Bake for 5 minutes in the preheated oven, or until cheese has melted.