To prepare the chicken, remove any excess fat; pat dry, then transfer the pieces to a bowl and set aside.
To prepare the marinade, whisk together the yogurt, lemon juice, lemon zest, olive oil, garlic, ground cumin, dried oregano, paprika, ground cinnamon, ground ginger, cayenne pepper (if using), tomato paste, salt, and pepper in a mixing bowl until well combined.
Pour the marinade over the chicken and mix well, ensuring all the chicken pieces are thoroughly coated. Cover it tightly with plastic wrap, removing as much air as possible. Place it in the fridge and marinate for at least 4 hours or preferably overnight.
If using wooden skewers, soak them in water for 30 minutes before assembling the marinated chicken. Remove the marinating chicken from the fridge 20 minutes before grilling.
When ready to grill, turn the burners to medium-high and let them preheat for 10 minutes or until they reach 400 degrees F. Using tongs, dip a folded paper towel into the extra olive oil, then generously wipe the grates*.
Meanwhile, remove the chicken from the marinade and thread the chicken pieces through the skewer. Tap off any excess marinade. If you have a thin piece, fold it as you thread it so it will cook evenly. Do not pack the pieces too tightly, as this can lead to uneven cooking.
Place the skewers on the oiled grate in a single layer. Cover and cook for approximately 12-15 minutes, rotating every 5 minutes to achieve even browning and grill marks. If you have a meat thermometer, check doneness by inserting it into one of the chicken skewers. If the internal temperature reaches 165 degrees F., the chicken is done.
Remove the skewered chicken from the grill and loosely cover with aluminum foil for at least 10 minutes before serving.