Season the filet steaks with cumin, chili powders, and salt. Set aside.
Place red onion, vinegar, and ½ teaspoon salt in a bowl and stir to combine. Let sit for 15 minutes.
Heat oil in a small cast iron or stainless steel skillet over high heat until just starting to smoke.
Add steaks and cook without moving until well browned, about, about 2 minutes.
Flip and cook second side until brown, about 2 minutes longer.
Transfer to a large plate and let rest for 5 minutes.
Slice steak and serve with warmed tortillas, onions, cheese, cilantro, and lime wedges.
