Place the steak in a bowl, and the peppers and onions in another bowl (or Ziploc bag.
In a mixing bowl, whisk together the cilantro, lime juice, salt, garlic, chili powder, cumin, cayenne, and oil.
Pour most of the mixture over the steak, leaving about a tablespoon to be poured over the veggies. Toss the steak and vegetables in the oil(separately), cover, and let marinate in the fridge for at least one hour.
Preheat the grill to medium/high. Lay the steak strips on the hot grill and cook until grill marks have appeared on both sides(flip halfway through cooking) and meat is cooked through.
Place the veggies in a grill basket and cook, flipping as needed, until the veggies are soft and lightly caramelized.
Serve with tortillas, toppings, and cilantro chimichurri.
FOR THE CHIMICHURRI:
Place all ingredients in a blender and process until the onions and cilantro and finely chopped and sauce is only lightly chunky. Serve with fajitas.