Clean, wash, pat dry, peel, and cut the arbi into round slices of equal size. Set aside in a colander till required.
Make a smooth paste of tomato and ginger using ¼ cup of water in a blender. Transfer to a bowl.
Next, heat ghee in a heavy bottom kadhai/pan. Fry the sliced arbi over medium heat till crisp and golden. Transfer to a plate and set it aside.
To the same pan, add cumin seeds, mustard seeds, and asafoetida. Fry for 20 - 30 seconds to release their aroma.
Next, add the tomato paste, salt, red chili powder, turmeric powder, and coriander powder. Fry it nicely over low heat until the oil starts separating from the masala. This takes 5 - 6 minutes.
Add remaining 1 Cup water, green chili, garam masala, and simmer the curry over low heat for 2 - 3 minutes.
Now, add the fried arbi slices and mix nicely. Cover and cook the curry over low heat for 5 minutes or till arbi is cooked.
Garnish arbi ki sabji with fresh coriander leaves.
Serve arbi ki sabji with puri or paratha.