In a large bowl, combine Greek yogurt, olive oil, lemon juice, minced garlic, cumin, paprika, turmeric, coriander, cinnamon, cayenne pepper, salt, and pepper. Mix well to create a marinade.
Add the chicken breasts to the marinade, ensuring they are well coated. Cover and refrigerate for at least 1 hour, or up to overnight for best flavor.
Preheat your grill or grill pan over medium-high heat. Remove the chicken from the marinade and discard the marinade.
Grill the chicken for about 6-7 minutes on each side, or until the internal temperature reaches 165°F. Remove from the grill and let it rest for 5 minutes before slicing.
While the chicken is resting, prepare the tahini sauce by whisking together tahini, water, lemon juice, and a pinch of salt in a small bowl until smooth.
To assemble the bowls, divide the cooked quinoa or rice among four bowls. Top with sliced grilled chicken, cherry tomatoes, cucumber, red onion, and parsley. Drizzle with tahini sauce.
Serve with pita bread on the side, if desired.