For the chutney

Take a heavy pan and add a teaspoon of oil. Add the groundnut, chana dal, garlic, green chillies, tamarind, and curry leaves. Roast on a low flame till golden. Remove the roasted ingredients from the pan and set aside on a plate to cool.
In the same pan, add the rest of the oil. Add the onions, tomatoes, ridge gourd, turmeric, and salt. Mix well. Cover the pan with a lid and cook for 10 minutes till the veggies are cooked and soft.
Finally, add a little jaggery and coriander leaves. Saute for a few seconds.
Set aside to cool a bit.
Transfer the peanut mixture to a heavy-duty blender and pulse several times to grind it to a coarse powder. Once the mixture is ground to a coarse powder, add the veggie mixture and grind again. Grind to a coarse texture. Do not grind to a fine paste.

Tempering the chutney

Heat oil in a small kadai and add the urad dal, mustard seeds, curry leaves, and dried red chillies. Let the mustard seeds crackle. Add the tempering to the chutney.

Serve with idli and dosai. It tastes good with rice too.