In a mixing bowl, whisk together the olive oil, fresh lemon juice, minced garlic, and all the spices: ground cumin, coriander, smoked paprika, turmeric, cinnamon, cayenne pepper, salt, and black pepper.

Slice the onions and layer them evenly across the bottom of your slow cooker.

Place the chicken thighs over the sliced onions, ensuring they cover the onion layer completely. Pour the marinade evenly over the chicken.

Cover the slow cooker with its lid and set it to cook on LOW for 6-7 hours or HIGH for 3-4 hours.

Once cooked, remove the lid and use two forks to gently shred the chicken directly in the slow cooker.

Spoon the warm shawarma chicken into warm pita bread or over rice, topping it with plain Greek yogurt and fresh parsley.