Boil 4 cups of water in a pan. Once water starts boiling, remove from flame and add rice noodles in it. Let it soak in this water for 5 minutes. Drain the water and set aside.
Heat oil in a frying pan and add mustard seed and a pinch of asafoetida.
When mustard seeds crackle, add peanuts and white lentil and saute till lentil turn brown. Add chopped ginger, chopped green chilies, curry leaves and saute for few seconds.
Now add cooked rice noodles, turmeric powder, salt to taste and mix well.
Remove from flame. Roll the lemon on the kitchen counter and then divide it into 2 halves. Take the juice and add it to the sevai.