Thinly slice the flank steak against the grain into bite-sized strips.
In a small bowl, whisk together the juice from the lime, chili powder, sea salt, and black pepper.
Toss the steak strips in the lime marinade and let sit for 5 minutes.
Heat the olive oil in a large non-stick skillet over medium-high heat.
Add the sliced red bell pepper and yellow onion, sautéing for 3-4 minutes until softened and slightly charred.
Push the vegetables to the side and add the steak to the pan, searing for 2 minutes per side until browned.
Remove the steak and vegetables from the pan and wipe the skillet clean.
Place the tortilla in the pan, sprinkle the cheddar cheese on one half, and top with the steak and vegetable mixture.
Fold the tortilla over and cook for 2 minutes per side until the exterior is golden and crispy.
Garnish with chopped fresh cilantro before slicing into wedges.