Steam or boil the asparagus until you can stab the thick end of one with a fork. Remove from the water and drain, reserving the cooking liquid. Cut off the tips and reserve. Then cut the stalks into small pieces.
Heat the butter in a wide 4-quart/4-l pot over medium-low heat. Add the onion and asparagus stalks and sauté until the onion is translucent. Add the rice and continue stirring