Make the chimichurri: In a food processor, combine the parsley, cilantro, garlic, red onion, paprika, vinegar, olive oil, salt, and pepper. Blend until smooth. Reserve half for drizzling on the fajitas. Place the remaining half in a large resealable plastic bag.
Marinate the steak: Place the steak in the bag with the marinade, squeeze out excess air, and seal. Rest at room temperature for up to 2 hours.
Make the peppers: In a large straight-sided pan with a lid, heat the oil over medium-high heat. When the oil begins to swirl, add the poblano, bell, and jalapeno peppers, and the onion. Season with a pinch of salt and a few grinds of pepper. Cook, stirring, until softened and slightly caramelized around the edges, 6 to 8 minutes. Add the beer, cover, and reduce the heat to medium. Cook until all the vegetables are plump and tender, about 10 minutes. Remove from the heat.
Grill the steak: Preheat a grill or grill pan to medium high. Remove the steak from the marinade and discard the marinade. Season the steak with a pinch of salt and a few grinds of pepper on both sides. Grill the steak, flipping just once, until cooked to medium rare, 5 to 6 minutes per side. Transfer the steak to a plate, cover loosely with aluminum foil, and let rest for 10 minutes before slicing.
Warm the tortillas: Preheat the oven to 200 degrees F. Wet your hands and rub each side of the tortillas with your hands, then stack the tortillas, wrap them tightly in aluminum foil, and place on the center rack of the oven until steamy, about 10 minutes ( or place them in a warmer).
Assemble the fajitas: Slice the steak into thin slices on the bias, against the direction of the muscle. Place a few strips of meat on each warmed tortilla and top with the peppers. Drizzle the reserved chimichurri over the top and fold loosely like a soft taco.
These peppers keep well in an airtight container in the refrigerator and are great with scrambled eggs in the morning, over grilled chicken or pork, or on a hot dog. Add a few capfuls of apple cider vinegar while you cook the peppers and serve them with fried fish.
Adapted from "Sunny's Kitchen: Easy Food for Real Life" by Sunny Anderson © Clarkson Potter 2013. Provided courtesy of Sunny Anderson. All rights reserved.