Slice the flank steak into thin strips across the grain and season evenly with sea salt, black pepper, garlic powder, and cumin.
Heat the olive oil in a large skillet over medium-high heat until it begins to shimmer.
Add the steak strips to the hot skillet and sear for 2-3 minutes until nicely browned and cooked through, then transfer to a plate and set aside.
In the same skillet, sauté the thinly sliced bell peppers and onions for 3-4 minutes until they become tender and slightly caramelized.
Wipe the skillet clean and place the whole wheat tortilla in the pan over medium heat.
Sprinkle half of the Monterrey Jack cheese over one half of the tortilla, then layer on the seared steak and sautéed vegetables.
Top the mixture with the remaining cheese and fold the tortilla in half to close.
Cook for 2 minutes per side until the tortilla is golden and crisp and the cheese has completely melted.
Remove from the heat, let rest for one minute, then slice into wedges and serve.