01 - Pat the chuck roast dry with paper towels and season generously on all sides with sea salt and freshly ground black pepper.
02 - Heat olive oil in a large skillet or Dutch oven over medium-high heat. Sear the beef on all sides until deeply browned, approximately 3 minutes per side.
03 - Transfer the seared beef to a slow cooker, or leave it in the Dutch oven. Scatter the thinly sliced onion, minced garlic, and chopped red chili pepper around and over the meat.
04 - In a mixing bowl, combine the crushed pineapple with its juice, tomato puree, brown sugar, apple cider vinegar, soy sauce, ground cumin, and smoked paprika. Stir until well blended, then pour the sauce evenly over the beef and aromatics.
05 - Cover and cook on low for 6 hours, or on high for 3 to 4 hours, until the beef is fork-tender and pulls apart with minimal effort.
06 - Remove the beef from the cooking liquid and shred it using two forks. Return the shredded meat to the slow cooker and toss thoroughly with the sauce to coat evenly.
07 - Lightly toast the sandwich buns in a dry skillet or under a broiler until golden on the cut sides.
08 - Mound the saucy pulled beef generously onto each toasted bun. Top with shredded red cabbage and fresh cilantro leaves. Add a smear of mayonnaise or aioli if desired. Serve immediately.