Slice the flank steak into thin, bite-sized strips and place them in a small bowl.
Season the steak with chili powder, smoked paprika, cumin, sea salt, and black pepper, tossing until evenly coated.
Heat half of the avocado oil in a cast-iron skillet over medium-high heat until shimmering.
Add the steak strips to the skillet and sear for 2-3 minutes until browned and cooked through, then remove and set aside.
Add the remaining oil to the same skillet along with sliced bell peppers and onions, sautéing until they are tender and slightly charred.
Wipe the skillet clean and return to medium heat; place the tortilla in the pan.
Sprinkle half the Monterey Jack cheese on one half of the tortilla, then top with the cooked steak and vegetables.
Add the remaining cheese over the filling and fold the tortilla in half.
Cook for 2 minutes per side until the tortilla is golden-brown and the cheese is fully melted.
Drizzle with fresh lime juice, slice into wedges, and serve immediately.