Marinate the chicken: In a large bowl, combine the yogurt, lemon juice, olive oil, tomato paste, garlic, and spices. Season the chicken with salt, then add it to the marinade and toss well until every piece is coated. Cover and refrigerate for 4–8 hours, or overnight for even more flavor.
Prepare the skewers: Preheat a gas grill to medium heat and lightly oil the grates. Thread the marinated chicken onto the skewers, folding any larger pieces if needed.
Grill the chicken: Place the skewers on the hot grill in a single layer. Cover and cook for 15–20 minutes, turning every 5–7 minutes, until the chicken is cooked through and nicely charred.
Air fryer method: Preheat the air fryer to 400°F (200°C). Arrange the chicken skewers in a single layer, leaving some space between them. Cook for 10–14 minutes, turning halfway through, until golden and cooked through. The chicken should reach an internal temperature of 165°F (74°C).