In a heavy based frying pan that can be tightly covered, melt the butter over medium-high heat. Stir in the rice and salt and cook, stirring constantly, until the rice begins to absorb the butter and becomes opaque but not brown.
Quickly add the remaining 1 1/2 cups boiling water, along with the saffron water. Cover immediately, reduce heat to low, and cook for 20 minutes, or until all of the liquid is absorbed. For best results, do not remove the lid while the rice is cooking.