Heat oil in a pan. Add the chopped onion to the hot oil, stir until they turn translucent.
Meanwhile, grind fennel seeds and garlic pods into coarse paste. Add the garlic and fennel paste, chopped tomatoes and turmeric powder to the onion, stir it well.
Once the oil gets separated from the vegetables, add the cleaned prawns, red chilli powder and curry leaves. Stir them until they change the colour. Close the pan with lid and cook on a medium flame. (Prawns may release water, so no need to add water). Check for the salt.
Cook until the water evaporates and the oil get separated.