Grate beet root. Grind that with salt, tamarind and red chilly in a mixer grinder.
Make seasoning with mustard seeds and udad dal
Add chopped onions to that and fry well
Add the grind beet root in that and fry again
Add salt and stir well
Remove from the fire and serve with dosa or eat with rice.
Note: You can replace beet root with carrot or cabbage and do the same to get more varieties of chutney.
If you don't like onion, you can avoid and prepare chutney without onion also.