Cut pork shoulder into 2 (4- to 5-inch-thick) pieces. Combine chile powder, black pepper, cumin, cloves, sugar, and 1 tablespoon of the salt in a small bowl. Sprinkle mixture over all sides of pork pieces. Heat oil in a large cast-iron skillet over high. Add pork pieces, and cook until deep golden brown on all sides, about 2 minutes per side. Place pork in a 5- to 6-quart slow cooker; add vinegar and oregano.
Cover and cook on LOW until pork falls apart easily when shredded with a fork, 8 to 10 hours.
Stir together tomato, red onion, lime juice, jalapeño, and remaining 1/2 teaspoon salt in a bowl. Chill at least 2 hours or up to 24.
Heat tortillas according to package directions. Shred pork in slow cooker with 2 forks; stir in paprika and cayenne. Serve pork on tortillas topped with salsa and cilantro.
These tacos were absolutely delicious. I am adding this to my repertoire.