In a pan take mustard oil, let it heat up. Next, add the gram flour and roast it for a few seconds until fragrant, remove from heat, and set aside.
In a bowl, take hung curd, add ginger garlic paste, garam masala, red chili powder, Kasuri methi, coriander powder, salt, pepper powder, and lime juice, and give it a nice whisk.
Next, add the prepared oil and gram flour mixture and mix everything properly.
Add the chicken pieces, rub and coat the chicken properly in the marinade, add the cubed bell peppers and onions, and let it rest for 6 hours.
Preheat the air fryer for 5 minutes at 180-degree C (350-degree F). Brush the basket with little butter and put the marinated chicken pieces in it. Brush a little butter on top. Cook for 4 minutes on one side, then turn and cook for another 4 minutes or until dark golden brown. Repeat with other pieces.
Next, put the marinated bell peppers and onion in the basket and cook for 3 minutes and transfer it to a plate along with the chicken.