Persian Rice

Place rice in a medium saucepan; add 2 teaspoons salt and cold water to cover by 2". Bring to a boil over medium heat; reduce heat to low and simmer for 5 minutes. Drain rice, reserving 3/4 cup cooking liquid.
Place saffron and 1/2 cup reserved cooking liquid in a small bowl; let saffron soften for 5 minutes. Place yogurt in a medium bowl and stir in remaining 1 teaspoon salt and saffron water. Add rice and stir to coat.
Melt butter in a large deep nonstick skillet over medium heat; swirl to coat bottom and sides of pan. Add rice, mounding slightly in center. Poke 6-7 holes in rice with the end of a wooden spoon. Cover with foil, then a lid. Cook, rotating skillet over burner for even cooking, for 10 minutes (do not stir). Reduce heat to low; cook, adding more reserved cooking liquid by tablespoonfuls if rice has not finished cooking when water evaporates, until a golden brown crust forms on bottom of rice, 20-25 minutes.
Remove lid and foil; invert a plate over skillet. Using oven mitts, carefully invert rice onto plate; use a heatproof spatula to remove any crust remaining in skillet.