Combine the spices and set aside.
Pierce the pork butt all over with a knife
Rub the spices all over the pork butt and into the slits you cut
Place the pork butt into the slow cooker
Combine the tomato sauce, red wine vinegar and chicken broth and our over the pork butt.
Add the sliced onions
Cook on high for 7-8 hours.
When the pork butt is done remove the bone and shred the meat