01 - Pat the beef chuck roast dry with paper towels. Season generously with salt and pepper on all sides, pressing the seasoning into the meat.
02 - Heat olive oil in a large skillet over medium-high heat. Sear the beef on all sides until deeply browned, about 2–3 minutes per side.
03 - Transfer the seared beef to the slow cooker. Add sliced onion, garlic, jalapeño, crushed tomatoes, beef broth, lime juice and zest, chili powder, cumin, smoked paprika, and oregano.
04 - Cover and cook on low for 8 hours, or until the beef is very tender and easily shreds with a fork.
05 - Remove the beef from the slow cooker. Shred using two forks, discarding any large pieces of excess fat.
06 - Return the shredded beef to the slow cooker and stir well to coat with the cooking juices. Taste and adjust seasoning if needed.
07 - Spoon the shredded beef into warmed tortillas. Top with diced red onion, cilantro, cheese, avocado, and extra lime juice as desired.