Place chicken cubes in a deep bowl. Add chilli powder, lemon juice and salt and mix well till the chicken cubes are evenly coated. Cover with a cling film and allow to marinate for half an hour, preferably in the refrigerator.
To make the marinade, place the yogurt in a muslin cloth. Gather in the edges and tie it up into a bundle and hang till all the water drains out.
Transfer the drained yogurt into a bowl. Add red chilli powder, clove powder, salt, ginger paste, garlic paste, lemon juice and garam masala powder. Whisk well to a smooth mixture.
Apply this yogurt mixture over the chicken cubes till they are well coated. Cover with cling film and refrigerate to marinate for three to four hours. Thread the chicken cubes onto skewers.
Heat oil in a non-stick grill pan. Place the skewers on the pan and cook, rotating the skewers for even cooking, for ten to twelve minutes. Baste with melted butter and cook for two minutes more.
Sprinkle chaat masala and serve with onion rings and lemon wedges.