Instructions : 

1. Heat oil in a pan and add cumin seeds and curry leaves.
2. Add onion and green chilli. Sauté until the onion becomes soft.
3. Add ginger-garlic paste and cook for 1 minute.
4. Add tomato, turmeric, chilli powder, coriander powder, and salt. Cook until the tomato becomes soft.
5. Pour in the coconut milk and simmer for 3–4 minutes.
6. Gently add the canned mackerel and cook for another 2–3 minutes.
7. Turn off the heat and serve hot with rice or roti.