Marinate prawns with salt, turmeric powder, and lemon juice. Rest for 15–20 minutes.
Heat oil in a pan and fry prawns until golden on both sides. Remove and keep aside.
In the same oil, fry sliced onions until golden. Add more oil if needed.
Add ginger-garlic paste and sauté until raw smell disappears.
Add all spices and coconut milk. Cook until masala is well roasted.
Add fried prawns and mix gently.
Add water, cover, and cook for 5–7 minutes on low to medium flame.
Check doneness, then add coriander leaves and green chilies.
Serve hot with roti or rice.