01 - In a large bowl, combine the yogurt, lemon juice, ginger-garlic paste, tandoori masala, cumin, coriander, turmeric, chili powder, smoked paprika, vegetable oil, salt, and black pepper. Whisk until smooth and uniform.
02 - Add the chicken cubes to the marinade and toss until every piece is thoroughly coated. Cover the bowl tightly and refrigerate for at least 4 hours, preferably overnight, for maximum 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 skewers, leaving a small gap between each piece. Alternate with onion slices and bell pepper pieces if desired.
05 - Preheat an outdoor grill, grill pan, or oven broiler to medium-high heat.
06 - Place skewers on the grill and cook for 15 to 20 minutes, turning every 4 to 5 minutes and basting with melted butter or ghee, until the chicken is cooked through and lightly charred at the edges.
07 - Remove skewers from the grill, sprinkle generously with chopped fresh cilantro, and serve immediately with lemon wedges alongside naan, rice, mint chutney, or raita.