One of the most reliable places to eat in Jaffna, Cosy Restaurant has been serving Tamil food to locals and the occasional traveller for many years. The crab curry here — served with a mountain of rice, several small vegetable dishes, and a rasam that clears the sinuses — is the thing to order. It arrives in a clay pot and should be eaten with your hands. The lunch thali is excellent value and typically sells out by 1pm.
The room is simple and the service is brisk, which is part of what makes it honest. This is where people from Jaffna actually eat rather than where they take visitors to impress them, which is usually a better recommendation.