1. Fill and boil your kettle. Tip the lentils into small pan and add 300ml boiling water. Bring to the boil, then cover with a lid, turn the heat down and simmer on a low heat for 20 mins. When cooked, drain the lentils.
2. Meanwhile, peel and thinly slice the onions and the garlic, if you're using it. Pour 2 tbsp olive oil into a large pan and warm it on a medium-low heat. Add the onions and garlic to the pan with a pinch of salt and pepper. Fry for 20 mins, stirring occasionally, till golden and soft. When the onions and garlic are soft and glossy, scoop half out onto a plate and set aside.
3. Finely grate the lemon zest. Stir 1 tsp each cumin seeds, ground coriander and turmeric into the pan. Add the cinnamon stick, cloves, lemon zest and 1 tbsp demerara sugar. Stir to mix. Fry for 1-2 mins till the onions smell aromatic. If you haven't already drained the lentils, check they're cooked and drain them now.
4. Add the rice and drained lentils to the pan. Pour in 350ml boiling water and give everything a good stir. Bring to the boil, pop a lid on the pan, then turn the heat down to low and cook for 15 mins till the rice has absorbed the water and is tender. When cooked, take the pan off the heat and set aside for 5-10 mins, lid on, to steam the rice and finish cooking it.
5. Just before serving, stir the reserved onions through the rice and lentils. Taste and add more salt or pepper or a squeeze of lemon juice if needed. Serve with wedges of lemon on the side, topped with spoonfuls of yogurt and coreiander if you'd like.
6. A crisp finish^
This dish is traditionally topped with crispy pan-fried onions. To give your caramelised onions that extra crunch, just before serving warm 3 tbsp olive oil in a frying pan on a high heat. Add the reserved fried onions and sizzle for 4-5 mins, stirring frequently, till brown and crispy. Scoop them into a bowl lined with kitchen paper to drain, then spoon the onions over the rice and lentils to serve.