Step 1

Heat the oven. Arrange a rack in the middle of the oven and heat to 500°F. (Use convection if you have it.) Line a rimmed baking sheet with aluminum foil, then fit a wire rack inside it.

Step 2

Make the spice rub. Place the salt, brown sugar, paprika, black pepper, chili powder, smoked paprika, dry mustard, garlic powder, onion powder, cornstarch, cayenne, and celery seeds in a small bowl and stir to combine.

Step 3

Brown the pork. Pat the pork dry with paper towels. Evenly coat the pork with 1/2 of the rub, then place it on the wire rack fat-side up if possible. Roast until the pork is sizzling with a bit of char on the edges, about 10 minutes, but don't let the spices burn and turn acrid.

Step 4

Prep the slow cooker. Meanwhile, place the onions in a 6-quart or larger slow cooker. Sprinkle with the remaining rub. Pour in the cola, vinegar, and Worcestershire.

Step 5

Slow cook the pork 14 to 16 hours. Transfer the pork to the slow cooker. Cover and cook on the LOW setting until the pork is soft enough to pull apart with a spoon, 14 to 16 hours.

Step 6

Shred the meat. Transfer the pork to a large bowl and let stand until cool enough to handle. Pull the meat apart into large chunks or shred with a fork, discarding any bone, connective tissue, and large clumps of fat.

Step 7

Strain the liquid. Fit a fine-mesh strainer over a medium bowl. Pour the cooking liquid through the strainer and discard the solids. If you are serving immediately, spoon off as much fat as possible from the surface. For best results, refrigerate until the fat solidifies and collects on top, then scrape off and discard the fat (keep the meat covered and refrigerated during this time).

Step 8

Moisten the meat. Toss the meat with enough defatted cooking liquid to moisten. Serve the meat warm, or let cool, cover, and refrigerate to use in other recipes.