01 - Whisk together olive oil, lime juice, minced garlic, cumin, chili powder, smoked paprika, salt, and black pepper in a bowl. Add the sliced beef and toss thoroughly to coat. Allow to marinate for at least 15 minutes, or refrigerate up to 2 hours for enhanced flavor development.
02 - Heat a large skillet or cast-iron pan over medium-high heat until hot. Add a small amount of oil if the pan appears dry.
03 - Arrange the marinated beef strips in a single layer without overcrowding. Sear for 2-3 minutes per side until well-browned and cooked through. Transfer beef to a plate and tent with foil to keep warm.
04 - Add the sliced bell peppers and onion to the same pan. Sauté for 5-7 minutes, stirring occasionally, until vegetables are tender and display light charring.
05 - Return the seared beef to the skillet. Toss with the sautéed vegetables until evenly combined and heated through, approximately 1-2 minutes.
06 - Heat tortillas in a dry skillet for 30 seconds per side or microwave in a damp paper towel for 20-30 seconds until pliable.
07 - Spoon the beef and vegetable mixture into warm tortillas. Garnish with chopped cilantro, fresh lime juice, and desired toppings such as salsa, guacamole, or sour cream.