Rinse rice in several changes of cold water in a large bowl until water runs clear. Drain in a large sieve. Bring 3 quarts water and salt to a boil in a 4- to 5-quart heavy pot, then add rice and cook, uncovered, stirring occasionally, 5 minutes from time water returns to boil. Drain parboiled rice in a sieve. Clean and dry pot. Melt butter with coriander seeds and pepper in pot over low heat, stirring to combine, then sprinkle rice into pot, mounding it in center. Make 5 or 6 holes in rice to bottom of pot with round handle of a wooden spoon and sprinkle rice with zest. Cover pot with a kitchen towel and a heavy lid. Fold edges of towel up over lid (to keep towel from burning) and cook rice over low heat, undisturbed, until tender and a crust forms on bottom, 30 to 35 minutes. Remove from heat and let rice stand, tightly covered and undisturbed, 30 minutes. Discard zest (or save for garnish) and spoon loose rice onto a platter. Season rice with salt, then break crust into pieces and scatter over rice.