In a small bowl, mix together chili powder, cumin, paprika, garlic powder, onion powder, salt, and black pepper.
Rub the spice mixture all over the beef chuck roast, making sure to cover all sides.
Place the beef in a slow cooker and add beef broth, lime juice, orange juice, tomato paste, jalapeno pepper, onion, and garlic.
Cover and cook on low for 8-10 hours, or until the beef is tender and easily shreds with a fork.
Remove the beef from the slow cooker and shred it using two forks.
Return the shredded beef to the slow cooker and stir it into the cooking liquid.
Cook for an additional 30 minutes on low to allow the flavors to meld.
Serve the shredded beef on warm tortillas with your favorite toppings, such as shredded cheese, diced tomatoes, avocado, and cilantro.