Aromatic basmati rice is spiced with saffron and cooked to form a crispy crust on the bottom in this Persian cuisine staple.
Place the rice in a large bowl and cover with cold water. Swish the water a couple times with your hands, then rinse the rice in a large mesh sieve or colander with small drainage holes. Repeat the process until the water runs clear. Put the rice back in the bowl and cover with 3 cups cold water along with 1 tablespoon salt; give it a couple of stirs. Let soak 1 hour.
Add 8 cups water and the remaining 3 tablespoons salt to a large saucepot and bring to a boil. Drain the rice and add it to the boiling water, giving a stir. Let cook until the water begins to bubble again, about 3 minutes. Check the rice: It should be al dente (soft on the outside with a slight bite in the center). If still not al dente, cook 1 to 2 minutes more. Drain the rice and rinse briefly with warm water. Taste the rice: If it seems too salty, rinse it again. Set the rice aside in the sieve.
Stir the saffron and 3 tablespoons hot water together in a small cup.
Place a 6-quart nonstick pot over medium-high heat. Add the ghee and half of the saffron water. Swirl to melt and completely coat the bottom and slightly up the sides of the pot. When the ghee begins to sizzle, add enough rice to coat the bottom of the pot evenly, about 1 ½ inches high. Press down gently but firmly with a spatula or a measuring cup to compact the rice and press about 2 inches up the sides to form a crust. Gently spoon the remaining rice over the top, forming a small mound in the center. Using the handle of a wooden spoon, make 6 deep holes to vent steam down into the rice, stopping before hitting the bottom of the pot. Cover the pot with the lid and cook for about 10 minutes (you will see steam coming from underneath the lid).
Whisk the melted butter together with the remaining saffron water. Remove the lid from the pot, being careful not to drip condensation back into the pot. Turn the heat to low. Wrap the lid with a clean kitchen towel, securing at the top to keep loose ends away from the fire. Drizzle the saffron butter into the rice. Cover with the lid and continue to cook, rotating the pot every so often for even browning, until the crust is deeply golden brown, about 30 minutes. Remove from the heat and remove the lid. Let stand 5 minutes, then check that the bottom is detached from the pot with an offset spatula, loosening it gently if necessary. Place a platter over the top of the pot, using kitchen towels to hold the sides, and in one quick motion, invert the pot and the rice onto the platter. Serve immediately.