Place the oil in a large pot and set over medium heat. When it is hot, add the onions, garlic, red bell pepper and carrots. Season with salt and pepper. Cook until the onions are tender, about 6 to 7 minutes.
Add the beef, lentils, tomatoes, broth, achiote, cumin and stir to combine. Increase the heat to high and bring to a boil.
Reduce the heat to low, cover and cook over low heat until the meat and lentils are tender, approximately 35 to 40 minutes.
Add the potatoes, cilantro and cooked quinoa. Simmer for about 25-30 minutes or until the potatoes are tender.
Add the chopped cilantro and season with salt to your taste. Serve with aji and avocado.