Pour the water into an electric kettle. If you've got a thermostat on the kettle, set it to 212 degrees F (100 degrees C) and bring to a boil.
Combine the rice, butter, and salt in a 2- to 3-quart saucepan and set over high heat. Cook, stirring constantly, until the rice just begins to take on color and smells like nutty popcorn. Very carefully pour in the boiling water and immediately cover with the lid. Reduce the heat to its lowest setting and cook for 20 minutes.
Remove from the heat, uncover, and gently fluff the rice with a fork. Let stand for 3 to 5 minutes before serving.