Heat the oil in a pan. Sauté the onion for approx. 5 mins., add the tomato puree and saffron, cook briefly. Pour in the water, bring to the boil and season with salt.
Rinse the rice in a sieve under cold running water until the water runs clear, then drain well. Transfer the rice to the prepared dish. Pour the stock over the top.
Approx. 20 mins. in the centre of an oven preheated to 200°C. Serve with yoghurt.