Prepare the following, adding each to a food processor fitted with the blade attachment as you complete it: Coarsely chop 1/2 medium yellow onion (about 1 cup). Coarsely chop 6 fresh parsley sprigs (about 1/3 cup). Add 3 garlic cloves, 1 tablespoon tomato paste, 1 tablespoon pomegranate molasses if desired, 1 tablespoon baharat spice, 1 1/2 teaspoons kosher salt, 1 teaspoon ground cumin, 1/2 teaspoon ground allspice, and 1/2 teaspoon cayenne pepper if desired.
Pulse until the onions are coarsely chopped, about 10 (1-second) pulses. Scrape the mixture into a large bowl. Add 1 pound lean ground beef or ground lamb. Using your hands or a flexible spatula, mix until evenly combined; do not overmix.
If your pitas are very stiff, stack and wrap 4 pocketed pitas in a damp paper towel and microwave until just slightly warmed and pliable, about 30 seconds. Cut each pita in half to create half moons. Divide the filling evenly between the pita pockets (about 1/4 cup per pita half) and spread to create an even layer.
Heat a large cast iron skillet or grill pan over medium-high heat. Brush 2 tablespoons olive oil over the outsides of all of the pita (both sides). Working in batches, place in the pan and cook until the outside of the arayes are browned and crisp, and the filling is cooked through, 3 to 5 minutes per side. Reduce the heat as needed if the pitas are browning too quickly before the filling is cooked. Transfer to a platter and cover to keep warm while you cook the remaining arayes. Meanwhile, make the sauce.
Finely grate 1 garlic clove into a small bowl. Juice 1 medium lemon into the same bowl until you have 2 tablespoons. Add 1/2 cup plain Greek yogurt, 2 tablespoons tahini, and 2 tablespoons water. Stir to combine. Thin out with more water a tablespoon at a time as needed until the consistency is smooth and creamy. Taste and season with kosher salt and black pepper as needed. Garnish with sumac, if using. Serve the arayes with the sauce for dipping.