Thinly slice the flank steak against the grain into bite-sized strips.
In a small bowl, combine the sea salt, black pepper, cumin, and garlic powder, then toss with the steak strips to coat evenly.
Heat half of the avocado oil in a large cast-iron skillet over medium-high heat.
Add the sliced bell peppers and onions to the skillet, sautéing for 4-5 minutes until tender-crisp and slightly charred, then remove and set aside.
Add the remaining oil to the same skillet and sear the steak strips for 2-3 minutes until browned and cooked to your desired level of doneness.
Wipe the skillet clean and place the tortilla inside over medium heat.
Layer half of the shredded cheese on one half of the tortilla, followed by the steak, peppers, and the remaining cheese.
Fold the tortilla in half and press down slightly with a spatula.
Cook for 2 minutes per side until the tortilla is golden-brown and the cheese is fully melted.
Transfer to a cutting board, let rest for one minute, then slice into three wedges and serve.