Chop chicken thighs into 1 ½-inch pieces.
Combine the yogurt, olive oil, lemon juice, lemon zest, minced garlic, paprika, salt, garlic powder, sumac, black pepper, dried mint, cumin, oregano, and cinnamon in a bowl. Stir till fully combined.
Add the chicken into the bowl and toss till each piece is covered in marinade. Allow to marinate for 25 minutes at room temperature (or in the refrigerator for up to 24 hours).
Heat a grill or grill pan to medium-high heat (375 degrees F).
Thread chicken and onion pieces onto metal skewers, making sure not to overcrowd.
Cook on grill or in grill pan for 4 to 7 minutes on each side. Some pieces will char, but make sure the chicken doesn’t overcook or burn. The chicken will be done when it reaches a temperature of 165 degrees F on an instant-read thermometer.
When the chicken has cooked, remove it from the grill and allow it to rest for 5 minutes before garnishing with optional toppings.
Serve alongside rice or pita bread.