Make the guiso: In a medium sauce pan, heat the oil over medium heat. Add the onions and cook for about 5 minutes, add the rest of the ingredients and cook for about 10 minutes, stirring occasionally. Set aside.
Place a pot over medium-high heat. Add the water, beef boullion, ground cumin, guiso and achiote. Stir to combine. Reduce the heat to low and simmer for 15 minutes.
While the broth is simmering, make the meatballs: In a medium bowl, combine all the meatball ingredients and using your hands, mix well until combined.
Divide meat mixture equally into 12 portions and roll into balls with your hands. Place in a plate and set aside.
Add the meatballs to the broth. Simmer for 20 minutes, add the rice and vegetables and cook for 20 minutes more. Stir in the fresh cilantro and top with avocado. Serve.