In a bowl, mix together the olive oil, lime juice, chili powder, cumin, garlic powder, onion powder, smoked paprika, salt, and pepper. This will be your marinade.
Add the sliced flank steak to the marinade and toss to coat well. Let it marinate for at least 30 minutes (or up to 2 hours in the fridge for deeper flavor).
Heat a large skillet or grill pan over medium-high heat. Once hot, add the marinated steak in a single layer, cooking for about 3-4 minutes on each side until browned and cooked to your desired doneness. Remove the steak and set aside.
In the same skillet, add the sliced bell peppers and onion. Sauté for about 5-7 minutes until they are tender and slightly charred, stirring occasionally.
Return the steak to the skillet with the sautéed peppers and onions, and toss everything together to combine and heat through for another minute.
Adjust seasoning if needed.
Serve the steak and peppers in warm tortillas, garnished with fresh cilantro and lime wedges on the side for squeezing over.
Notes
Marinate the steak for deeper flavor if time allows.