01 - In a mixing bowl, combine olive oil, lemon juice, minced garlic, cumin, smoked paprika, coriander, oregano, cayenne pepper, salt, and black pepper. Add the sliced chicken and toss until evenly coated. Let marinate for at least 15 minutes at room temperature, or refrigerate for up to 8 hours for deeper flavor penetration.
02 - In a small bowl, whisk together the Greek yogurt, lemon juice, fresh dill, grated garlic, and season with salt and pepper to taste. Cover and refrigerate until ready to serve to allow the flavors to meld.
03 - Heat a grill pan or large skillet over medium-high heat. Add the marinated chicken in a single layer and cook for 6 to 8 minutes, stirring occasionally, until the chicken is cooked through and lightly charred on the edges. Remove from heat and set aside.
04 - Warm each pita bread briefly in a dry skillet over medium heat for about 30 seconds per side, or microwave for 15 to 20 seconds until soft and pliable.
05 - Open each warm pita and layer with shredded romaine lettuce, diced cucumber, halved cherry tomatoes, and sliced red onion. Top generously with the cooked chicken and drizzle with the prepared yogurt sauce.
06 - Serve the assembled pitas immediately while the chicken is still warm. Offer extra lemon wedges on the side for squeezing over the top.