Take a cup of water in a pan, bring it to rolling boil. When it is boiling, include red chillies and switch off. Let the chillies soak in hot water for about 15 minutes.
After soaking time chillies would have turned soft, drain all the water from them. Keep aside. Next take 1/2 cup of chopped onion in a pan and saute till it turns translucent.
Next add soaked red chillies, tamarind, jaggery, salt, cumin seeds, curry leaves, coriander leaves, garlic, and sauteed onion in to mixer jar.
Grind all the ingredients together in to thick paste. Next heat a pan with oil and mustard seeds. Let the mustard sizzle, then include ground chutney and saute for 2 minutes. Switch off.
Spicy and gorgeously colored red chilly chutney is ready to serve with any rotti.