Place rice in a large bowl. Wash rice well, till the cloudy water runs clear. Allow rice to soak in water for 30 minutes to 1 hour.
In a large stockpot, bring 8 cups (about 2 litres) of water to a boil. Add salt to water.
Drain rice and transfer to stockpot of boiling water. Decrease the heat to medium-high and allow the rice to boil for 5-7 minutes. At the 5-minute mark, take a grain and if it easily breaks between your finger and thumb, remove from the flame (cooking times can vary across rice brands). The grains should be soft on the outside but still have a firm core.
Drain the rice immediately through a fine-mesh colander and rinse briefly with warm water to remove excess salt. Scoop out 1 cup (230g) of cooked rice and set aside.
In a small bowl, bloom saffron: whisk the saffron powder with ¼ cup (60 ml) hot water. Set aside.
In a large bowl, combine parsley, cilantro, dill, and scallions. Gently toss. Add the reserved 1 cup of rice to the herb mixture and fold gently to combine, being careful not to break the rice grains.
In a large 10-in/23-cm non stick pot, heat 3 tablespoons neutral oil and 2 tablespoons butter over medium heat. Swirl to coat the bottom evenly. The butter should melt and become foamy but should not brown. If it starts to darken too quickly, reduce the heat slightly.
Add the saffron water and the rice you had set aside, gently mixing so each grain is coated with saffron. Flatten this mixture into an even layer—this will form the golden crust (tahdig).
Add the herb and rice mixture to the pot, spreading it evenly. Using the handle of your wooden spoon, poke 4-5 holes into the rice, so the rice has room to steam (but don’t pierce all the way to the bottom of the pot). Place a paper towel or tea cloth on top of the pot and seal shut with lid. Make sure to tie the corners of the tea cloth on top of the pot’s lid. (without piercing the tahdig layer).
Drizzle ¼ cup / 60ml water evenly over the rice. Place a clean tea towel or paper towel over the pot, then secure the lid on top. If using a tea towel, tie the corners up away from the heat to prevent burning.
Cook over medium-high heat for 7 minutes to develop the golden crust. You should hear a gentle sizzling sound—this is a sign that the tahdig is forming. If you smell burning, reduce the heat slightly. Reduce the heat to low and steam for 40 minutes. Avoid lifting the lid during this time to retain steam.
Turn off the heat and let it rest for 5-10 minutes (do not remove the lid yet). Place a large platter over the pot. Holding the pot handles firmly, carefully invert it onto the platter to release the rice. If the tahdig does not release easily, place the pot back on low heat for 1-2 minutes to loosen it.