In a pan heat oil and roast black gram dal and dried red chilli.
add in 1 finely chopped onion and garlic, sauté till they turn slightly golden in colour.

Now add tomato and mix well after add salt and cover and cook for 3-4 min
cool completely and transfer to the blender.
add in small piece tamarind for a taste and blend to smooth consistency.

Now prepare the tempering by heating 2 tsp oil.

Also add in mustard seeds, asafoetida and few curry leaves and allow the tempering to splutter.

Onion tomato chutney ready and serve along with idli or dosa.