If you like it sweeter, add 1 tsp of Jaggery. This step is completely optional.
Transfer the mixture to a blender and blitz until a smooth chutney is obtained.
Adjust Salt to suit the taste.
Transfer the chutney into the serving bowl.
Heat oil in a small pan and add mustard seeds, urad Dal, curry leaves and red chillies. Allow the mustard seeds to splutter and now season the chutney with the prepared tempering.
Serve onion tomato chutney with dosa & idli.
Notes
KITCHEN NOTES:Dried Red Chilly can be increased or decreased to suit the level of spiciness.Add Jaggery for the hint of sweetness. ( optional )Adding Ginger to Tomato Onion Chutney is completely optional.