In a skillet, warm the oil with the annatto seeds over moderate heat until bright orange, 3 minutes; strain into a large saucepan.
In a food processor, puree the onion, garlic, bell pepper, tomato and cilantro. Reheat the annatto oil. Add the onion mixture and ham and cook over moderately high heat until fragrant. Stir in the stock, rice and cumin; season with salt and pepper. Bring to a boil; stir in the peas. Reduce the heat to moderately low, cover and simmer for 15 minutes. Remove from the heat and let stand, covered, for 3 minutes, then transfer to bowls and serve.