Season the flank steak evenly on both sides with sea salt, black pepper, garlic powder, and smoked paprika.
Heat a cast-iron skillet over medium-high heat with half of the avocado oil.
Sear the steak for 4-5 minutes per side until cooked to your preferred doneness, then remove from the pan and let it rest for 5 minutes.
In the same skillet, add the remaining oil along with the sliced red bell pepper, green bell pepper, and yellow onion.
Sauté the vegetables for 5-7 minutes until they are tender and slightly charred, then remove from the pan.
Thinly slice the rested steak against the grain into bite-sized strips.
Wipe the skillet clean and place the whole wheat tortilla inside over medium heat.
Sprinkle half of the Monterey Jack cheese over one side of the tortilla, then layer on the steak strips and sautéed vegetables.
Top with the remaining cheese and fold the tortilla in half.
Cook for 2-3 minutes per side until the tortilla is golden brown and the cheese is fully melted.