Beat the egg whites in a big bowl till it is frothy and starts making soft peaks.
Whip the yolk in another bowl till it is creamy and then combine them both together. Keep aside.
Heat 2 tablespoon oil in a pan add chopped onions,saute them for a minute, till it turns golden brown.
Add the chopped bell peppers (red,green and yellow),and the green chillies and give it a good toss.
Cook for 3-4 minutes so that the vegetables are properly cooked, add 1 teaspoon of red chilli powder and salt to taste. Take it off the heat and keep aside.
Take a fresh pan, heat up, combine 2 teaspoon oil and 1 teaspoon butter.
Pour the egg batter in the pan. Be careful to turn the heat to the lowest.
Cover the pan with a lid and let it cook for 2 mins.