Cook the onion in the hot, melted butter in a heavy pot over a medium flame. Stir and sauté it until it is almost translucent. Do not let it brown in the slightest.
Put in the rice and salt. Stir and sauté gently for 1 minute.
Pour in the measured water and bring to the boil. Cover tightly, reduce the heat to very, very low and let the rice cook for 2