Heat some oil in a pan.
Add mustard seeds, hing, and curry leaves to the pan.
Then add chopped onion and saute till golden brown.
Add the rest of the chopped vegetables like bell peppers, carrots, cabbages and tomatoes.
Now add turmeric, garam masala, red chilli powder, a little vinegar, soy sauce and ketchup. Let it cook for 1-2 minutes.
Cut the idlis into small pieces and mix them in the pan. You can use leftover idlis or prepare fresh. Cook for 3-4 minutes.
Enjoy the hot Masala Idli with fresh coriander and lemon juice.