Start by cooking the barbacoa meat according to your favorite recipe (click for recipe). The key is to let it slow-cook until it's tender and full of flavor.
In a blender, combine the tomatillos, chopped white onion, garlic cloves, chipotle peppers, chopped cilantro, ground black pepper, A1 steak sauce, and lime juice. Blend until smooth. Taste and adjust seasoning as needed.
While the barbacoa finishes cooking, warm the flour tortillas on a skillet over medium heat for about 30 seconds on each side or wrap them in a damp towel and microwave for 30 seconds.
To assemble the tacos, take a warm tortilla and layer in the barbacoa meat. Top with shredded red cabbage, a generous spoonful of pico de gallo, and drizzle with the tomatillo salsa. Finish with fresh cilantro and a squeeze of lime.
Serve your Barbacoa Tacos with extra lime wedges and salsa on the side. Gather your friends and family and dig in!