Chop the onion and keep it aside.

Heat 1 teaspoon of oil in a pan.

Add cumin seeds and dry red chillies and cook for 10 seconds.

Add black urad dal (split) and cook until golden.

Turn off the heat and drain in a bowl.

Add another 1/2 teaspoon of oil to the same pan.

Add onions and cook for 4 to 5 minutes until softened.

Turn off the heat and let it cool down.

Put the cooked urad dal, cumin, and dry red chillies in a mixer grinder and grind them into a coarse powder.

Add the cooked onions, tamarind paste, and jaggery to the grinder.

Add a little water and grind to a smooth or slightly coarse chutney consistency.

For the tempering, heat the remaining 1/2 teaspoon of oil in a small pan.

Add mustard seeds (rye) and curry leaves.

After 10 seconds, add the tempering to the chutney and mix well.

Serve South Indian onion chutney with masala dosa or ghee dosa.