Sear the Roast: Heat olive oil in a skillet over medium-high heat. Season the beef with salt and pepper, then sear each side until golden brown, about 3–4 minutes per side.
Layer Ingredients: Place sliced onions and minced garlic in the bottom of your crock pot. Add the seared roast on top.
Mix the Sauce: In a bowl, combine pineapple chunks (with juice), chopped chipotle peppers, beef broth, tomato paste, soy sauce, smoked paprika, and cumin. Pour over the beef.
Slow Cook: Cover and cook on Low for 8–9 hours or High for 4–5 hours until the beef is fork-tender.
Shred and Serve: Remove the roast, shred the meat with two forks, then return it to the slow cooker and stir to coat in the sauce.
Assemble Bowls: Serve the shredded beef over rice. Garnish with cilantro, avocado slices, and a squeeze of lime.