Season the roast. Sprinkle both sides of the chuck roast generously with salt and black pepper.

Sear the meat. Heat 1–2 tablespoons of oil in a large skillet over medium-high heat (cast iron works great). Once hot, sear the roast for 2–3 minutes per side until a deep brown crust forms.

Transfer to the slow cooker. Place the seared roast into your slow cooker.

Sauté the aromatics. In the same skillet, add the chopped onion. Cook for about 3–4 minutes, stirring often, until softened and golden. Add the garlic and cook for another 30 seconds, just until fragrant.

Combine everything. Remove the skillet from heat and add the onions and garlic to the slow cooker. Pour in the tomato sauce, chili powder, cumin, salt, pepper, bouillon cubes, green chiles, both types of beans, and cayenne (if using). Stir gently to combine around the roast.

Cook low and slow. Cover and cook on LOW for 8 hours, or until the beef is fall-apart tender.

Shred and serve. Shred the chuck roast using two forks (either right in the slow cooker or on a cutting board). Stir everything together, taste, and adjust salt or chili powder if needed.

Serve and enjoy. Ladle into bowls and top with shredded cheese, sour cream, or chopped green onions.