Put rice into a large bowl, cover with cold water, and swish around with your hand until water clouds. Drain. Repeat process until water remains clear, 4–5 more times. Return rice to bowl. Add 1 tsp. of the salt and enough water to cover rice, then set aside to let soak for 1 hour.
Put 3 cups water and remaining salt into a medium nonstick pot and bring to a boil over medium-high heat. Drain rice, add to pot, and boil until most of the water has been absorbed and rice is almost tender, about 8 minutes. Drain rice; set aside.
Return pot to medium-high heat. Add half the butter and 2 tbsp. water, and spoon rice into pot, forming a conical shape. Drizzle remaining butter and 2 tbsp. water over rice; cover pot with a clean dish towel, then cover pot with a lid. Reduce heat to medium-low and steam rice for 30 minutes.
Uncover pot and fluff rice, keeping golden rice crust on bottom of pot intact. Spoon fluffed rice onto a large platter. Put an inverted plate inside pot and carefully invert rice crust onto plate, then transfer to top of rice.