Clean the sardines and make gashes on both sides. Let it drain.
Make a paste of 1 tsp of chilly powder, a pinch of turmeric and required salt.
Apply the paste on both sides of the sardines and keep aside for 15 minutes.
Fry the marinated sardines and keep aside.
Grind the ingredients to be ground: cumin, remaining chilly powder, mustard seeds, remaining turmeric powder, ginger, garlic and onion pieces to a fine paste.
Heat the oil again and fry the ground paste for sometime.
When oil has accumulated on top, add tomato pieces and onion. Saute well.
Pour 1/4 cup water, sugar, vinegar and required salt.
Boil the mixture and then cook in low heat until the gravy acquires a thick consistency.
Yummy sardine vindaloo is ready and serve hot.