Put the garlic paste, chilli powder, and lemon juice in a large shallow dish, season with salt and mix well. Add the chicken breasts and rub evenly all over to coat. Cover and allow to marinate in the refrigerator for 1 hour.
Now, place the chicken in a tray, add the flour and mix well. Add the oil and mix again.
Prepare a tandoor or charcoal grill for moderate heat, or alternatively preheat the grill (broiler) to medium. Thread the chicken onto several metal skewers and place a tray underneath to collect any juices.
Roast in a moderately hot tandoor, over a charcoal grill or under the hot grill for 6 minutes, or until half done.
Remove the skewer from the heat and hang it up for about 2-3 minutes to allow any excess moisture to drain out completely. Put the skewer in a dish, baste with melted butter, and roast again in the tandoor or under the grill for a further 4 minutes, or until cooked.
Transfer the chicken to a plate and serve hot.