Heat the oil and fry the onion seeds for about 30 seconds. Add the onion and fry for about 5 minutes.
Add the tomatoes, pepper, ginger, garlic, chilli powder, coriander, potato, salt and peas, and stir-fry over a medium heat for a further 5 minutes. Add the rice and stir-fry for about 1 minute.
Pour in 750ml/1 1⁄4pt water and bring to the boil, then reduce the heat to medium. Cover and cook for a further 12–15 minutes. Leave the rice to stand for 5 minutes, and serve hot.