Place the beef tenderloin cubes, pork loin cubes, and masa harina in a plastic bag, and shake to coat the meat. Heat the olive oil in a large skillet over medium-high heat, and cook and stir the meat cubes until evenly browned, about 10 minutes.
Place the meat, red onion, tomatoes, green chile peppers, beef broth, cumin, potato, garlic, oregano, cilantro, cayenne pepper, salt and white pepper in a slow cooker. Cook on Low until the meat is tender, about 8 hours.
