Generously season hanger steak with salt, pepper and taco seasoning. Leave at room temperature for 30 minutes. In Dutch oven over medium high heat, add olive oil and sear hanger steaks well on each side. Add 1 cup beef broth, cover, turn heat down and simmer, turning occasionally. Add more liquid if needed. This will take 1 1/2-2 hours. Let cool and shred. In a skillet over medium heat, add olive oil and caramelize the onions until golden, about 15-20 minutes. Set aside.
In another skillet, lightly warm tortillas on each side with a little oil or put on a sheet pan in the oven at 350 degrees for 5 minutes until warm and pliable.
To make the enchiladas, preheat oven to 400 degrees. Pour 1/3 cup enchilada sauce into a 9 x 13 inch baking dish. Cover each tortilla with sauce, a few tablespoons of meat, peppers, corn, cheese and then roll tortillas. Pour remaining sauce over the rolled enchiladas and finish with 1 cup of cheese. Bake for25-30 minutes until cheese is melted and sauce is bubbling. Garnish with chopped cilantro, scallions and a dollop of sour cream. Serves 4-6.