Easy Crock Pot Steak Taco Filling

1 1/2 to 2 lbs. flat iron steak 1.25 oz. pkt. taco seasoning 10 oz. can diced tomatoes with green chilies, undrained 1 C. thin sliced red onion Spray your crock pot with cooking spray. Add the meat, seasoning, diced tomatoes and red onion. Cover and cook on low for 8 hours. Shred with a fork before serving.