Thinly slice the flank steak against the grain into bite-sized strips.
In a small bowl, combine the chili powder, smoked paprika, cumin, 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 caramelized.
Add the sliced red bell peppers and red onions to the pan, sautéing for another 3 minutes until the vegetables are tender-crisp.
Deglaze the pan with lime juice and stir in the fresh cilantro, then transfer the mixture to a plate.
Wipe the skillet clean and place the tortilla in the pan over medium heat.
Sprinkle the Monterey jack cheese over one half of the tortilla and top with the steak and pepper mixture.
Fold the tortilla in half and cook for 2 minutes per side until the exterior is golden brown and the cheese is completely melted.
Slice into wedges and serve immediately.