Preheat the oven to 200°C/Fan 180°C/Gas 6. Tip the rice into a large bowl. Cover with cold water and whisk for 1-2 mins till the water is cloudy. Drain and cover with fresh water. Leave to soak.
Peel the squash. Cut it in half lengthways and scoop out the seeds with a spoon. Compost or plant them. Slice the squash into 1cm-thick half moons. Place on a baking tray. Peel the onion and cut into quarters. Drizzle with 1 tbsp oil and season. Slide into the oven to roast for 30 mins.
Crush 5 cardamom pods lightly with the back of a knife to open them slightly. Set a large saucepan on a high heat. Drizzle in 1 tbsp olive oil. Tip in the cardamom pods, 6 curry leaves, 1 cinnamon stick and 2 tsp mustard seeds. Fry for 2 mins, stirring. Remove from the heat.
Drain and rinse the rice. Add it to the pan. Add a large pinch of the saffron and a pinch of salt. Cover with 300ml boiling water. Stir well and clamp on a lid. Simmer for 8 mins till the rice is tender and the water has been absorbed. Remove the pan from the heat and take off the lid to cool slightly.
While the rice is cooking, make a small cross in the bottom of each tomato – cutting through the skin only, not the flesh. Place in a bowl and cover with boiling water. Drain the water and cover with cold water. When cool enough to handle, peel the skin from the tomatoes and discard the skin. Roughly chop the tomatoes and place in a bowl.
Cut the half-cucumber into thin slices and add to the bowl with the tomatoes. Finely chop the coriander stalks and add to the bowl. Set the leaves aside.
Zest and juice the lemon into a small bowl. Squeeze in 2 tbsp tamarind paste. Add 1 tsp sugar, ½ tbsp oil and whisk well. Pour over the tomatoes and cucumber and toss.
Halve the pomegranate. Hold one half in the palm of your hand, cut side down over a bowl. Lightly tap the pomegranate with a wooden spoon. The seeds should tumble into the bowl. Repeat with the other half. Fold half the seeds through the rice.
Spoon the warm saffron rice onto two plates. Top with the roasted squash and onions. Serve with the tomato and tamarind salsa. Scatter over the remaining pomegranate seeds and coriander leaves.