I have used small onions you can use big one also.
No need to have sambar if you are in a hurry just plain rice and this dry curry will be more than enough.
If you don't like to add urad dhal you can avoid it.
Fine chopping of beetroots helps the vegetable to cook quickly.
Be aware when adding water if you add it in excess then the colour will change and flavour will also be lost.
Vegetable should be cooked correctly always with a little crunch.