01 - Heat olive oil in a large skillet over medium-high heat. Brown beef cubes on all sides, about 5 minutes. Transfer to slow cooker.
02 - Add diced onion, green bell pepper, and jalapeño (if using) to the same skillet. Sauté for 3 to 4 minutes until softened. Add garlic and cook 1 minute more. Transfer vegetables to slow cooker.
03 - Add kidney beans, crushed tomatoes, beef broth, chili powder, cumin, smoked paprika, oregano, black pepper, salt, and cayenne pepper (if using) to the slow cooker. Stir to combine.
04 - Cover and cook on LOW for 6 to 7 hours or on HIGH for 3 to 4 hours, until beef is tender and flavors are developed.
05 - Taste and adjust seasoning if necessary. Serve hot, garnished with cilantro, shredded cheddar, sour cream, or sliced green onions as desired.