Preheat an outdoor grill or grill pan to medium heat. Add steak and cook until charred on one side, 3-4 minutes. Flip and cook an additional 4-5 minutes, until internal product temperature reaches 160°F on a meat thermometer. Remove from heat and set aside to rest, 5 minutes.
Meanwhile, wash, dry, and pick cilantro leaves off the stems. Wash, dry, and cut lime into wedges. Peel, halve, and mince onion. Place all three toppings on a plate and set aside.
While the steak is resting, preheat a skillet over medium-high heat. Once the skillet is hot, working in batches, add tortillas and cook until lightly charred, about 30 seconds per side. Remove to a plate and loosely cover with aluminum foil to keep warm.
Thinly slice steak against the grain.
Divide warmed tortillas between plates, then top with steak strips. Crumble cheese over top, drizzle with salsa verde, then sprinkle with cilantro and onion. Serve with lime wedges for squeezing and enjoy!