Melt the butter in a large pan over a medium heat and cook the onion with a large pinch of salt for 10 mins until golden. Stir in 1 tsp cracked black pepper and 1/2 tsp ground turmeric, and cook for 1 min more. Stir in the basmati rice, rinsed, then pour over the vegetable or chicken stock or water, and stir well. Cover and bring to the boil, then remove the lid, stir, cover again, and reduce the heat to low. Cook for 2 mins, then turn the heat off and set aside for 10 mins. Stir, then cover again and leave to stand for a final 5 mins.