Heat up a bowl full of water in a kettle and place this water on the stove for boiling with some salt.
Add vermicelli to it and let it cook until soft.
Strain this water and run the vermicelli under cold water.
In a separate pan, heat the oil and add the mustard seeds and let them splutter.
Add the chopped onion, curry leaves, ginger, green chilli and turmeric. Let the onions become soft.
Add the tomato and fry until they become soft.
Finally, add the cooked vermicelli to it and mix.
Add the lemon juice after removing the dish from the flame and mix and serve hot.