Grind all the ingredients mentioned under ground masala to a smooth paste and set aside.
In a pan, heat coconut oil and add ginger and onions. Saute the onions till they turn light golden brown and add tomatoes. Cook the tomatoes for 5-7 minutes till they break down easily with the back of a spoon.
Add the ground masala and salt to the pan and bring it to a boil. Reduce the flame and simmer the masala for 10-15 minutes till the colour deepens slightly.
Add the prawns to the gravy and cook them for 7-8 minutes. Sprinkle curry leaves on top, mix well and turn off the heat.
Let the curry rest for 5 minutes before serving with steamed rice.