Mix together chili powder, garlic powder, onion powder, cayenne powder, oregano, paprika, cumin, pepper, and cornstarch.

Put onions, peppers, and steak in the slow cooker. Top with seasoning mixture, garlic, lime juice, and diced tomatoes.

Cover and cook on high for 4 hours or on low for 8 hours.

Remove steak from the slow cooker and broil for 4-5 minutes until crisp.

Slice into thin strips and mix back in with the rest of the ingredients in the slow cooker.

Serve with tortillas and toppings of choice.