In a large bowl combine ground beef, onion, breadcrumbs, milk, eggs, chili powder, paprika, garlic powder, ½ teaspoon cumin and ¾ teaspoon sea salt. Using a tablespoon, scoop meat out and form into meatballs.
Preheat a skillet to medium and spray well with oil. Cook meatballs until browned. Coat a slow cooker with cooking spray and transfer meatballs. In a blender, combine tomatoes, chicken broth, garlic, coriander, chipotles and remaining ½ tsp cumin and ¾ teaspoon sea salt. Process until smooth. Pour on top of meatballs and cook on high for 3 hours.