Combine the onion, bell pepper, tomatoes, beans, salt, cumin, garlic powder, chili powder, and meat in a 6-quart slow cooker, stirring to combine.
Cover and cook on high for 5-6 hours or low for 7-8 hours, or until the meat is very tender.
Remove the beef, shred into large pieces with two forks, then return to the slow cooker, stirring to combine.
Add the lime juice, stir, and taste, adding additional lime juice or salt if you like. Serve with hot sauce and whatever toppings you prefer.