Cut boneless mutton into small cubes. Marinate them with raw papaya paste, ginger garlic paste, yogurt and all the other ground dry masalas, turmeric, red chilli powder, mace and nutmeg powder, black pepper powder and salt, for at least 4-5 hours or leave it overnight in the refrigerator. Heat oil and fry finely sliced onion till crispy. Strain oil and crush the onion. Add the crushed onion to the marinated mutton. Lastly, add the remaining mustard oil of fried onion and mix well.
Hook the cubed mutton in skewers and cook them in a grill pan or pre-heated oven. Pre-heat oven to 180°C and grill for 30 minutes. Turn over and cook for another 20 minutes till evenly browned both sides. Brush oil when nearly done. Garnish with chopped coriander and serve with sliced onion and tomato with a sprinkling of lemon juice.
