Dry roast red chillies and fennel seeds in a kadai until fragrant, then cool.

Grind the cooled red chillies, fennel seeds, and coconut with a little water into a smooth paste.

Heat sesame oil in a kadai and temper with fennel seeds and curry leaves.

Add sliced onions and tomatoes, then add turmeric powder and salt.

Cook on low flame until the tomatoes become soft and pulpy.

Add 1 cup of water to the mixture.

Add the ground masala paste and mix well.

Simmer the gravy for 3-4 minutes.

Transfer the Chettinad Vengaya Kosu to a serving bowl.

Garnish with chopped coriander leaves and serve hot.