This is a classic style of serving basmati rice in Iran. Saffron rice, a delicate red spice, turns gold when it touches water. We followed this recipe, from Fine Cooking.
2 cups white basmati rice
Fine sea salt
3 Tbs. canola or vegetable oil
1/2 tsp. saffron threads
1 Tbs. unsalted butter, cut into quarters, softened
Put the rice in a medium bowl and add cold water to cover by at least 1 inch. Soak at room temperature, swishing the rice around a few times, for 30 minutes. Drain through a medium-mesh strainer, and rinse under cold water until the water runs clear.
In a 4- to 6-quart pot, combine 8 cups water and 1 oz. (about 2 heaping Tbs.) salt.
Bring to a boil over high heat, add the rice, and return to a boil. Lower the heat to medium high and cook, stirring occasionally, until the rice is almost tender but the center is still opaque and not yet fully cooked, about 5 minutes. (Test by breaking a grain in half.) Drain through the medium-mesh strainer and rinse under cold water to cool. Drain well. Heat a 5-quart heavy-duty pot or Dutch oven, preferably measuring about 9-1/2 inches across, over low heat for about 2 minutes. Add the oil, swirling to coat the bottom of the pot. Spread 2 cups of the rice evenly over the bottom of the pot, and press down hard on it with a flexible spatula or the flat bottom of a measuring cup to compact it. Sprinkle 1/4 tsp. salt over the rice.
Add the remaining rice to the pot, centering it in the middle of the bottom layer of rice. Use your hands to shape the rice into a pyramid. Use a chopstick to poke several holes in the rice pyramid.
Cover the pot with its lid, turn the heat up to medium low, and cook, undisturbed, for 10 minutes. Reduce the heat to low; if you have a heat diffuser (also called a flame tamer or simmer ring), put it under the pot. Uncover the pot and place a folded kitchen towel over the pot, making sure the ends don’t touch the heat source. (Or use a damkoni; see tip below) Cover tightly with the lid. Cook until the rice on top is tender, about 50 minutes.
Meanwhile, grind the saffron in a mortar and pestle. Add 1 Tbs. hot water and set aside to steep.
Without disturbing the tahdig, gently spoon 1 cup of the rice into a small bowl and the rest onto a serving platter. Using a fork, gently toss the rice on the platter with the butter and season to taste with salt. Toss the rice in the bowl with the saffron water, and spoon it over the white rice.
Check that the underside of the tahdig is golden brown by gently lifting an edge with an offset spatula. If very pale, cook a few more minutes. Loosen the sides and bottom with a butter knife or a small offset spatula, and flip it onto a plate. (If it clings, remove it in pieces with a spatula.) Serve the tahdig whole or broken in pieces along with the rice.