Grind together the ingredients listed under 'to grind' to a fine paste using 1/2 tbsp water.
Heat oil in a pan and add finely sliced onions, chopped ginger & garlic. Cook it till the onions become soft. Add the ground paste to this and fry for a few minutes, till the oil starts appearing. Add the sliced tomatoes & tamarind pulp to this and cook for 2-3 minutes. Add coconut milk & salt to this. Let it boil. Add cleaned prawns, & curry leaves. Cook till the prawns are done and the gravy is thick.
Serve hot with rice.
Notes
I used coconut oil for this recipe. You can adjust the qty of tamarind pulp to suit your taste. Adding 1 cup of thick coconut milk gives you a thick gravy. If you're like us and need litres of gravy, I suggest you add at least 1 1/4 cups of coconut milk. In Camelia Punjabi's recipe, there is a final tempering with pearl onions & curry leaves. I haven't done it but I think it adds a special touch. Please keep in mind that it takes sometime for the flavor to set in, so make provisions accordingly.