Slice the flank steak against the grain into very thin strips and place them in a small bowl.
Toss the steak strips with chili powder, ground cumin, garlic powder, sea salt, and black pepper until evenly coated.
Heat the olive oil in a large cast-iron skillet over medium-high heat until shimmering.
Add the steak to the skillet and sear for 2-3 minutes until browned and caramelized, then remove the steak and set aside.
In the same skillet, sauté the thinly sliced bell peppers and onions for 3-4 minutes until tender-crisp.
Squeeze the fresh lime juice over the vegetables, stir in the cooked steak, and remove the mixture from the pan.
Wipe the skillet clean, place the tortilla in the pan, and sprinkle the shredded cheddar over one half.
Top the cheese with the steak and pepper mixture, fold the tortilla in half, and cook for 2 minutes per side until the exterior is golden and crispy.
Garnish with fresh cilantro before slicing into wedges and serving.