Wash and clean the mackerel by cutting the head, fins, tail, and tummy. Cut each mackerel into 3 to 4 pieces or more depending on the size of mackerel.
Marinate the mackerel pieces by applying red chili powder, turmeric powder and salt and keep it aside in fridge for 15-20 minutes.
Grind the grated coconut, red chilies, and tamarind together by adding ½ teacup water and make thick gravy with consistency thicker than chutney. Just one round in mixer/grinder is enough. See the recipe picture, it shows how thick the coconut should be ground. It should give you a faint idea.
To a kadai and add the ground mixture from the mixer/grinder, 2 slit green chilies and marinated mackerels.
Slightly crush "teffal" seeds using mortar-pestle and add them to the sukha gravy in kadai.
Add the kokum petals and cook this till mackerels get cooked.
Check the salt and adjust accordingly.