Sprinkle beef liberally on both sides with steak seasoning and chili powder. Allow to sit for about half an hour to come to room temperature.
Allow grill to warm up until very hot, turn down to medium high, then place beef on to cook. Turn as necessary to keep from overcooking, and remove from heat when an instant read thermometer reads 140 degrees. Cover tightly with foil for at least 10 minutes to rest.
If not grilling, preheat oven to 425 degrees. Heat large cast iron pan over medium high heat until very hot; add about 1 tablepoon of vegetable oil and warm until the oil is slightly smoking. Add beef to pan, and sear for about two minutes per side. Put cast iron pan in oven and allow to cook until instant read thermometer reads 140 degrees. Remove from oven, wrap tightly with foil and allow to rest for at least 10 minutes.
Slice beef against grain, on the diagonal and add any juices that remain.
Taco Sauce
Combine taco sauce and steak sauce until well mixed. Put in squeeze bottle.
Lettuce Layer
Shred romaine very finely using a knife. Combine salad dressing with chipotle powder and mix well. Toss romaine with dressing.
Cheese
Combine cheddar and blue cheese in small bowl.
Assembly
Place soft taco inside hard taco.Place lettuce inside tacosAdd beef slicesAdd cheese layerDrizzle taco sauce across tacosEnjoy!!