For the refrito: Place the peppers, tomatoes, cilantro and onions in a food processor and pulse until blended. Add in 3 tablespoons of the achiote oil and season the mixture with salt and black pepper. Stir everything together and chill until needed. Set aside 1/2 cup for the arroz amarillo, and then reserve the rest for another use.
For the arroz: Heat the oil in a pot over medium heat. Add 1/2 cup refrito, achiote powder and turmeric and saute for 2 to 3 minutes. Stir in the rice until evenly coated with the refrito mixture. Stir in the hot chicken stock and bring to a boil. Boil for about 10 minutes, and then reduce the heat to a simmer, cover the pot, and continue to cook the rice for 20 minutes. Chill the rice before serving.