Blend tomatoes, 1 onion, 1 clove garlic, and adobo sauce in a blender or food processor until smooth.
Heat oil in a large skillet over medium heat; cook and stir tomato mixture in hot oil until fragrant, about 10 minutes. Stir in chicken stock and continue to cook for 10 minutes more.
Meanwhile, blend tomatillos, eggs, 1 small onion, chipotle peppers, 2 cloves garlic, chicken bouillon, and cilantro in a blender or food processor until smooth. Transfer mixture to a large bowl and add beef, pork, and rice; stir to combine. Roll meat mixture into walnut-sized balls.
Transfer meatballs to tomato mixture; simmer until meatballs are no longer pink in the center, 15 to 20 minutes.
