In a bowl, combine chicken thighs, yogurt, lemon juice, olive oil, minced garlic, cumin, paprika, turmeric, cinnamon, cayenne pepper (if using), salt, and black pepper. Mix well to coat the chicken evenly.
Cover the bowl and refrigerate for at least 30 minutes, or preferably for 2-4 hours, to allow the flavors to meld.
Preheat your grill to medium-high heat. If using a grill pan, heat it over medium-high heat with a little oil.
Grill the marinated chicken for 6-8 minutes per side, or until cooked through and slightly charred. The internal temperature should reach 165°F (74°C).
Once cooked, let the chicken rest for a few minutes before slicing it thinly against the grain.
Warm the pita bread on the grill or in a dry skillet.
Assemble the shawarma: Fill the warm pita bread with shredded lettuce, diced tomatoes, cucumber, sliced red onion, and the grilled chicken. Drizzle with tahini sauce and garlic sauce.
Notes
Serve immediately for the best flavor and texture. You can also serve this as a bowl with rice or quinoa instead of pita bread.