Pour rice into a large bowl and fill with water. Rinse several times until the water runs clear, about 6-7 times and then soak the rice for 1 hour.
In a small pot, add lentils and 1 1/2 cups of water and bring to a boil. Once boiling, reduce to a simmer and cook lentils for about 10-15 minutes or until liquid has evaporated and lentils are tender. Season with salt and pepper and set aside.
In another pot, add rinsed rice and 4 cups of water. Boil rice until it is half way cooked and soft on the outside but still firm in the middle, about 10 minutes. You don't want to cook the rice fully because it will continue to cook later. When done, drain and rinse and set aside.
In the same pot you cooked the rice that is now empty, drizzle olive oil and saute chopped onion until caramelized. Then add barberries (or dried cranberries) salt, 1/2 teaspoon turmeric and 1/2 teaspoon cinnamon. Toss to combine and remove mixture to a bowl and set aside.
Wipe out the pot for any residual onion and drizzle with olive oil to coat the bottom and bring to medium heat. Add 1/2 teaspoon of turmeric and stir in the oil and lay potatoes in an even layer.
Mix lentils and rice together and add that on top of potatoes.
Then add the barberry-onion mixture and dried figs and lay on top of rice.
Drizzle saffron water over the top of everything and poke holes with the back of a large wooden spoon or chopstick. This will help the steam to escape and the bottom to get crispy.
Next, cover the lid with a clean towel and close lid on pot. Cook on high for about 10 minutes so the potato gets crispy then decrease heat to low for 20 minutes so the rice is fully cooked. The potato should be crispy and rice flurry and cooked through.
When done, remove lid and serve rice with potato tahdig on the side.