In a large Le Creuset French Oven, bring 3 cups of water to a boil. Add 3 tbsp kosher salt. At the same time, rinse the rice in a colander until the tap water runs clear. Add rice to boiling water, and stir continuously until the grains are parboiled (about halfway cooked, about 5 minutes). Lightly drain and set aside.
Prepare 3 small bowls. In the first, pour ½ cup just-boiled water over saffron threads to soak. In the second, combine rosewater with the raisins. In the third, combine cinnamon, cardamom, cumin, orange zest, apricots and barberries (or cranberries), and a pinch of salt.
In a small non-stick skillet or pan, lightly toast the almonds and pistachios with 1 tbsp of butter. Set aside.
Add another 1 tbsp of butter to the skillet and sautée the onion with a little bit of salt and a tsp of the saffron water. Add in the remaining contents of the two other small bowls (fruits and spices) and stir well to combine.
Going back to the French Oven, bring to medium heat, and melt the rest of the butter to coat the bottom of the pot. Spread half of the parboiled rice over the bottom, followed by half of the onion-fruit-spice mixture, and then the remaining rice. Leave uncovered and cook for 5-8 minutes.
Drizzle the remaining saffron water over the rice and put on the lid. Turn the heat to low and leave on the stove for 30 minutes undisturbed. Top with almonds, pistachios, parsley and pomegranate, or other suitable nuts and fruits of your choice.