Slice the flank steak into very thin strips against the grain.
In a small bowl, combine the chili powder, cumin, garlic powder, sea salt, and black pepper.
Toss the steak strips in the spice blend until evenly coated.
Heat the avocado oil in a large non-stick skillet over medium-high heat.
Add the steak to the skillet and sear for 2-3 minutes until browned and juicy.
Add the thinly sliced bell peppers and red onions to the skillet, sautéing for another 3 minutes until softened.
Squeeze the juice of half a lime over the steak and vegetable mixture, then remove from the pan.
Wipe the skillet clean and place the tortilla in the pan over medium heat.
Sprinkle half of the cheese over one side of the tortilla, top with the steak and veggie mixture, then add the remaining cheese.
Fold the tortilla in half and cook for 2 minutes per side until the exterior is golden brown and the cheese is fully melted.
Slice into wedges and serve immediately.