Tip the rice into a bowl. Pour over enough cold water to cover it. Tip the lentils into a separate bowl and cover that with cold water too. Leave them both to soak for around 15 mins.
Peel and finely chop the onion. Peel and dice the carrots. Roughly chop the tomatoes. Peel and grate the garlic and turmeric. Finely grate or pare the zest from the lemon. Juice it.
Warm 1 tbsp olive oil in a pan. Add the onion. Season. Fry over a low heat for 8-10 mins. Stir often till the onion is golden but hasn’t picked up too much colour – keep the heat low.
Stir in the garlic, turmeric, lemon zest and the carrots. Cook for about 5 mins. Stir every so often till the carrot has started to soften. Drain the lentils (they’ll have sucked up a lot of the water).
Stir the lentils and tomatoes into the pan with 350ml hot water from the kettle. Bring to the boil. Turn the heat down. Pop on a lid. Simmer for 30 mins till the lentils are soft and thick. Stir every now and then.
Fill the kettle and boil it. Drain the rice. Tip it into a pan. Pour in 300ml hot water. Add salt. Cover. Bring to the boil. Turn the heat down. Simmer for 25 mins till the rice is cooked and the water has been absorbed.
Stir the spinach into the korma till it wilts. Add the lemon juice. Taste and adjust the seasoning if you think it needs it. Serve with the rice.