The night before cooking, combine all ingredients except for the salt, pepper, cilantro, and tortillas in the removable insert of the slow cooker and refrigerate overnight.
The next day, let the insert set at room temperature for 30 minutes before cooking or dump the bowl into the insert to begin cooking right away.
Cover and cook on low for 6 to 8 hours or high for 3 to 4.
Ladle into bowls for serving and garnish with chopped cilantro and serve with tortillas.