Place saffron in a small bowl. Add 1/2 cup boiling water; steep.

Melt butter in a skillet that can be tightly covered over medium-high heat. Stir in rice and salt; cook, stirring constantly, until rice begins to absorb butter and becomes opaque, but do not let rice brown.

Quickly pour in remaining 1 1/2 cups boiling water and saffron water. Cover immediately, reduce heat to low, and cook until all liquid is absorbed, about 20 minutes. For best results, do not remove the lid while the rice is cooking.