Slice the flank steak against the grain into thin strips.
In a bowl, combine olive oil, lime juice, minced garlic, cumin, chili powder, salt, and pepper.
Add the steak to the marinade and let it sit for at least 15 minutes.
Heat a skillet over medium-high heat.
Add the marinated steak to the skillet and cook for 5-7 minutes until browned.
Remove the steak and set aside.
In the same skillet, add sliced bell peppers and onions.
Sauté the vegetables for about 5 minutes until softened.
Return the steak to the skillet and mix with vegetables.
Warm the tortillas in a separate pan or microwave.