01 - In a large bowl, combine the yogurt, lemon juice, ginger-garlic paste, tandoori masala, ground cumin, ground coriander, turmeric, chili powder, smoked paprika, vegetable oil, salt, and black pepper. Whisk until smooth and well blended.
02 - Add the cubed chicken to the marinade and toss to coat every piece evenly. Cover the bowl with plastic wrap and refrigerate for at least 4 hours, or preferably overnight for the deepest flavor penetration.
03 - If using wooden skewers, submerge them in water for 30 minutes prior to grilling to prevent burning.
04 - Thread the marinated chicken pieces onto the skewers, leaving a small gap between each piece. Alternate with onion and bell pepper slices if desired.
05 - Preheat an outdoor grill, grill pan, or oven broiler to medium-high heat.
06 - Place the skewers on the grill and cook for 15 to 20 minutes, turning every 4 to 5 minutes. Baste generously with melted butter or ghee throughout grilling until the chicken is fully cooked through and develops slight charring on the edges.
07 - Remove the skewers from the grill, sprinkle with chopped fresh cilantro, and serve immediately with lemon wedges alongside.