In a mixing bowl, combine olive oil, lemon juice, minced garlic, cumin, coriander, paprika, cayenne pepper, salt, and black pepper. Add chicken shawarma and mix well to coat. Cover and refrigerate for at least 1 hour.

In a small bowl, mix Greek yogurt with a squeeze of lemon juice and a pinch of salt. Set aside in the refrigerator.

Preheat the grill. Grill the marinated chicken for about 6-8 minutes per side or until fully cooked. Remove from heat and let it rest for a few minutes before slicing.

Warm the pita bread on the grill. Spread a layer of yogurt sauce on each pita bread. Top with sliced grilled chicken, diced cucumber, tomato, sliced red onion, and shredded lettuce.

Roll up the assembled shawarma, secure with a toothpick if needed, and serve hot. Enjoy!