Place the flank steak in a baking dish or resealable bag. Place the peppers and onions in another dish or bag.
In a large bowl, whisk together the beer, oil, lime juice, sugar, worcestershire sauce, lime juice cumin, both chili powders, smoked paprika, salt, pepper and garlic cloves. Pour half of the mixture over the beef and the other half over the peppers/onions, tossing well to coat. Cover both dishes and refrigerate for a few hours or even overnight. Toss the steak and peppers every so often to coat in the marinade.
Heat the grill on the highest setting. Create two foil packets – I like to use two sheets of foil for each. Divide the peppers and onions between the foil packets, folding the edges of the foil up slightly. Cover the tops with a third piece of foil.
Place the pepper packets directly on the grill. Grill for 5 to 10 minutes, tossing once or twice. While the peppers are grilling, place the flank steak directly on the grill. If it’s about 1-inch thick, grill for 5 to 6 minutes per side to still have some pink in the steak. When you remove the steak from the grill, let it rest for 10 minutes.
After 10 minutes, slice the steak against the grain in to super thin strips. Serve the steak with the peppers on top – in your fajita vehicle of choice!
For the corn tortillas, we char them slightly on the grill or gas stovetop. For the salad, we serve all of the above on a BIG bed of greens. I usually don’t use any extra dressing, there is more than enough juice and flavor and salsa. For the nachos, before piling everything on top, I cover tortilla chips with a cup or so of freshly grated cheese (cheddar, monterey jack, etc). I add the steak and peppers and broil for a few minutes until the cheese melts, then continue with the rest of the toppings.