Heat oil, add mustard seeds and saunf (fennel seeds). Add finely chopped onions. Cook till transparent. Add chopped green chillies, salt and turmeric powder. Soak rice flakes in water for a minute. Drain water and squeeze lightly to drain away excess water. Add soaked poha to the masala and stir well. Cook for a minute. Serve hot garnished with lemon juice and corriander leaves.