In a large bowl, whisk together olive oil, lemon juice, minced garlic, cumin, coriander, paprika, turmeric, cinnamon, salt, and pepper.
Add chicken slices to the bowl and toss until evenly coated with the marinade.
Heat a large non-stick skillet over medium-high heat.
Add the chicken to the skillet in a single layer and cook for 8 to 10 minutes, turning occasionally, until the internal temperature reaches 74 degrees Celsius (165 degrees Fahrenheit).
Warm pita breads in a dry skillet or oven for 30 seconds per side until pliable.
Cut each pita bread in half or slice the top edge to create a pocket.
Distribute shredded lettuce, diced tomatoes, cucumber slices, and red onions equally among the pita pockets.
Stuff the cooked chicken shawarma into the prepared pita pockets.
Drizzle each pocket with tahini sauce and serve immediately.