Add chopped tomatoes and cook until they turn soft and mushy.
Now, add red chili powder, turmeric powder, coriander powder, cumin powder, garam masala, and salt. Mix well and cook for a few minutes until the oil starts to separate from the masala.
Add the mutton pieces to the masala and mix well, ensuring the masala coats the mutton evenly.
Cook the mutton on high heat for about 5-7 minutes, stirring occasionally.
Add enough water to cover the mutton pieces. If using a pressure cooker, close the lid and cook until the mutton is tender (about 20-25 minutes on medium heat after the first whistle).
If cooking in a pan, cover and simmer until the mutton is cooked through and tender, stirring occasionally. Add more water if needed during the cooking process.
Once the mutton is cooked, check for seasoning and adjust if necessary. Add slit green chilies and lemon juice, and mix well.