01 - Combine the sliced beef with olive oil, lime juice, garlic, cumin, smoked paprika, chili powder, salt, and black pepper in a bowl. Mix thoroughly to coat all pieces, cover, and let marinate for at least 15 minutes. For deeper flavor, refrigerate up to 2 hours before cooking.
02 - Heat 1 tbsp olive oil in a large skillet or grill pan over medium-high heat. Add the sliced bell peppers and onion, season lightly with salt, and sauté for 5-6 minutes until just tender and slightly charred. Transfer to a plate and set aside.
03 - Add the marinated beef to the same skillet. Cook for 3-4 minutes, stirring occasionally, until browned and cooked through. Avoid overcrowding the pan for proper searing.
04 - Return the sautéed peppers and onions to the skillet with the beef. Toss together for 1 minute to combine flavors and heat through completely.
05 - Heat the tortillas in a dry skillet for 30 seconds per side or microwave between damp paper towels for 20-30 seconds until pliable and warm.
06 - Spoon the beef and vegetable mixture into warm tortillas. Garnish with chopped cilantro and fresh lime juice. Add salsa, guacamole, or sour cream as desired.