Combine olive oil, minced garlic, lime juice, chili powder, cumin, paprika, salt, and pepper in a bowl.
Add steak to marinade and coat well. Refrigerate for at least 30 minutes.
Heat a skillet over medium-high heat. Pat steak dry and cook for 3-4 minutes per side.
Let the steak rest for 5 minutes before chopping into smaller pieces.
In the same skillet, sauté onions and bell peppers until softened.
Wipe skillet clean and reduce heat to medium.
Place a tortilla in the skillet, sprinkle cheese on one half, then add steak, vegetables, and optional toppings.
Fold the tortilla over and cook for 2-3 minutes until golden brown.
Flip and cook for another 2 minutes until cheese is melted.
Repeat with remaining ingredients and serve warm with guacamole, sour cream, or salsa.