Coat the entire surface of the pork tenderloin liberally with salt and pepper. Place the pork in the slow cooker.
In a small bowl, whisk together the vinegar, syrup, mustard, cumin, cayenne, nutmeg and apple butter. Pour the mixture over the pork and top with the thyme. Place the lid on the slow cooker and cook on high for 3 hours or low for 6-7 hours.
In a large bowl, mix the celery root, pomegranate seeds and apple. In a separate small bowl, whisk together the lime juice, vinegar, mustard, honey, olive oil, salt and pepper. Pour the dressing over the slaw and toss to combine. Store in the refrigerator, covered, until ready to use.
When the pork is done, shred it using two forks and toss with the remaining sauce.
To serve, spread a small amount of pork on a corn tortilla and top with the slaw. Drizzle with sour cream if desired and serve immediately.