Drain the soaked rice and achiote seeds and liquefy them together in a blender with 1/2 cup of the beef broth. Remove and set aside.
Liquefy the tomatoes and onion with another 1/2 cup broth. Heat the oil in a saucepan and fry the tomato and onion mixture 5 minutes. Add the rice and achiote mixture and continue cooking over low heat.
Mix ground pumpkin seeds with remaining broth and strain mixture into tomato sauce through a strainer or food mill, extracting as much as possible. Continue cooking until mixture thickens to a creamy consistency. Add salt to taste; set aside, keeping warm.
Sauté the meat quickly, until just done, place on plates and pour the pumpkin sauce over.