Heat the oil in a kadai; add the mustard seeds, cumin seeds, curry leaves and green chillies and stir till the seeds begin to splutter. Add the turmeric powder and chilli powder and sauté, making sure that the masala does not burn.
Add the onion and sauté till translucent. Add the rice and stir-fry till the masala is mixed well into rice. Add the peanuts. Sprinkle some water over the rice and cook, covered, for one minute over low heat.
Stir in the lemon juice, salt and sugar. Serve immediately, garnished with coriander leaves.