01 - Whisk together olive oil, lime juice, garlic, smoked paprika, cumin, chili powder, oregano, salt, and pepper in a large bowl. Add flank steak and toss to coat thoroughly. Cover and refrigerate for at least 20 minutes, up to 2 hours for enhanced flavor penetration.
02 - Heat grill or grill pan over high heat until properly preheated. Remove steak from marinade and allow excess liquid to drip off.
03 - Place steak on hot grill and cook for 4-5 minutes per side for medium-rare doneness, adjusting time based on preferred internal temperature. Transfer to cutting board, tent loosely with aluminum foil, and let rest for 5 minutes to allow juices to redistribute.
04 - While steak rests, heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add sliced peppers and onions, season with salt and pepper, and sauté until tender-crisp with slight charring, approximately 6-8 minutes.
05 - Heat tortillas on grill for 30 seconds per side or in a dry skillet until pliable and lightly toasted.
06 - Cut rested steak thinly across the grain at a slight angle to ensure tenderness.
07 - Arrange sliced steak and sautéed vegetables on a large serving platter. Accompany with warm tortillas, avocado slices, sour cream, salsa, fresh cilantro, and lime wedges for guests to build their own fajitas.