firstly, in a large kadai heat 2 tsp of oil and saute 1 tsp urad dal, 4 dried red chilli to golden brown.
add in 1 onion and 1 inch ginger. saute well.
also add 2 tomato and saute till tomatoes turn soft and mushy.
furthermore add ¼ tsp turmeric, small piece tamarind and ½ tsp salt. saute well.
now add ¼ cup coconut and cool the mixture completely.
transfer to the blender and blend to smooth paste. add water only if required.
now prepare the tempering by heating 2 tsp oil.
add in 1 tsp mustard seeds, ½ tsp urad dal, 2 dried red chilli and few curry leaves. allow to splutter.
pour the tempering over chutney.
finally, serve tomato onion chutney with idli, dosa or rice.