Heat 2 tbsp oil in a heavy bottomed vessel. Add the chopped onion and green chillis and fry till transparent. Add the ginger-garlic paste and curry leaves and fry for a minute. Add chopped tomatoes and fry for another 3 minutes.
Add the cleaned prawns, salt and mix well. Cook on medium heat for 5 minutes. Now add 1 cup of water and cook further covered with lid for 5-7 minutes on medium heat. Add garam masala pwd and mix well. Turn off heat and garnish with chopped coriander/cilantro leaves. Serve hot with steamed white rice or chapatis/rotis.