In a medium saucepan, add 2 tablespoons of the vegetable oil and heat. Add the onions and saute for 3 minutes, until soft and translucent. Add the garlic and saute for another 2 minutes. Add the saffron threads and saute for 1 minute. Season with salt. Add the rice and saute, stirring constantly for 2 minutes. Add the water and cover the pot. Lower the heat to simmer and cook for 20 minutes. Remove from the heat and let sit, covered for 5 minutes. Uncover and fluff with a fork. While the rice is cooking, in a saute pan, over high heat, add the remaining vegetable oil. When the oil is hot, add the tomatoes and the cayenne pepper. Saute for 5 minutes, or until the liquid begins to evaporate. Add the olives, shrimp and preserved lemons and cook until the shrimp turn pink and their tails curl completely, about 4 to 5 minutes. Be careful not to overcook. Season with salt and pepper. Add the shrimp mixture to the rice mixture and mix well. Check for seasoning. Garnish with almonds and parsley.
Recipe courtesy of Food Network