Heat the oil in a large saucepan over a medium heat. Add the onion, stir-fry for 6–8 minutes until very soft, then add the spices. Continue to stir-fry for 2–3 minutes until fragrant. Now add the rice and lentils, and stir-fry for a further 2–3 minutes.
Add the stock and coriander, season to taste and bring to the boil. Reduce the heat to low, cover the pan and cook gently for 10–12 minutes or until all the liquid has been absorbed. Remove from the heat and allow to stand, covered and undisturbed, for 10–15 minutes. Fluff up the grains with a fork and serve.