Mediterranean Tuna Melts

Name: Mediterranean Tuna Melts
Ingredients: 3 7-ounce cans oil-packed light tuna (preferably Italian); 1/2 cup chopped fresh parsley; 1/4 cup pitted kalamata olives, chopped; 1/2 small red onion, thinly sliced; Juice of 1 lemon; 1/4 teaspoon smoked paprika; Kosher salt and freshly ground pepper; 4 whole pitas, each split into 2 rounds; 4 ounces muenster or halloumi cheese, thinly sliced; 3 tablespoons extra-virgin olive oil; 3 cups baby arugula; 1 pint cherry tomatoes, halved; 2 Persian cucumbers, halved lengthwise and thinly sliced