How to Make It
In a large sturdy plastic bag, combine the chipotles, garlic, 2 tablespoons of the olive oil and the lime juice. Add the skirt steak and marinate for 30 minutes.
Preheat the oven to 250°. Heat a large cast iron skillet. Working with one at a time, add the tortillas to the skillet and warm quickly over high heat, turning once, until softened and heated through, about 15 seconds per side. Wrap the tortillas in foil and keep warm in the oven.
Heat 2 tablespoons of the olive oil in the skillet until almost smoking. Add the red and yellow peppers and cook over high heat, stirring, until starting to brown, about 3 minutes. Add the onions and cook, stirring until tender and lightly charred, about 5 minutes. Season with salt and pepper, transfer to a large plate and keep warm in the oven.
Add the remaining 1 tablespoon olive oil to the skillet and heat just until smoking. Pat the steak strips dry with paper towels. Add half the strips to the skillet in a single layer, season with salt and pepper and cook, turning once, until browned, about 2 minutes per side. Transfer to a plate and cook the remaining steak. Return all the meat to the skillet and cook, for 1 minute.
Mound the steak on a plate; serve with the tortillas, onions and peppers, avocado, sour cream, Pico de Gallo and cilantro. Let everyone assemble his own fajita.