In a medium-sized bowl, combine the lime juice, soy sauce, vegetable oil, minced garlic, ground cumin, chili powder, smoked paprika, black pepper, salt, and chopped cilantro. Whisk together until well combined.

Place the sliced skirt steak in a large resealable plastic bag or a shallow dish. Make sure the meat is thoroughly coated by pouring the marinade over it.

Seal the bag or cover the dish with plastic wrap and refrigerate for at least 30 minutes, or up to 4 hours for maximum flavor.

Over medium-high heat, preheat a large skillet or grill pan. Once hot, add the marinated steak strips in a single layer.

Cook for 3-4 minutes per side, or until the steak reaches your desired level of doneness. Remove from the skillet and set aside.

If necessary, add a little extra oil to the same skillet. Add the sliced onion and bell peppers. Sauté for about 5-7 minutes, or until the vegetables are tender and slightly charred.

Place the cooked steak and the sautéed vegetables back in the skillet. Toss everything together to combine and heat through for an additional 1-2 minutes.

Warm the flour tortillas in a dry skillet or microwave. Serve the beef fajitas immediately with sour cream, guacamole, salsa, shredded cheese, and lime wedges on the side.