Place the ground beef and pork in a large bowl. Add onions, garlic, scallion, red bell pepper, masarepa, eggs, cumin, salt and pepper. Mix well using your hands.
Form the meatballs and add them to the slow cooker along with the remaining stew ingredients. Mix everything together carefully so as to not break up the meatballs.
Cook on low 7-8 hours or on high 3-4 hours. Serve with white rice and avocado on the side.