On a baking sheet place the 3 chili peppers, whole, and broil in the oven for about 5 minutes or until they are charred. Place the chilis into a Ziploc bag and close it, letting the chilis steak for 15 minutes. Then remove the chiles, peel the skin, remove the seeds, and cut each chile into thin slices.
Cut the steak into slices (like in the picture) and place in a dish with the apple cider vinegar, salt and pepper. Chill for 15 minutes in the refrigerator.
Drain the marinade. Heat a cast iron skillet over medium high heat and add coconut oil. Sear each piece of steak for about 3-5 minutes on each side, or until cooked to your liking. Place on a plate.
Add the onions and poblano chiles to the cast iron and cook until onions are brown. Mix with vegetables with the steak, and serve hot!