Slice the flank steak into very thin strips against the grain to ensure tenderness.
In a small bowl, whisk together the lime juice, chili powder, smoked paprika, cumin, sea salt, and black pepper.
Toss the steak strips in the spice mixture until evenly coated.
Heat the olive oil in a large non-stick skillet over medium-high heat.
Add the sliced bell peppers and red onion to the skillet, sautéing for 3-4 minutes until softened and slightly charred.
Push the vegetables to the side and add the steak strips, searing for 2 minutes per side until browned and cooked through.
Remove the steak and vegetables from the skillet and wipe it clean.
Place the tortilla in the skillet over medium heat; sprinkle half of the Monterey Jack cheese on one side of the tortilla.
Top the cheese with the steak and vegetable mixture, then sprinkle the remaining cheese over the top.
Fold the tortilla in half and cook for 2 minutes per side until the exterior is golden brown and the cheese is melted.
Remove from heat, garnish with fresh cilantro, and slice into three wedges before serving.