Thinly slice the flank steak against the grain into bite-sized strips.
In a small bowl, combine the chili powder, smoked paprika, sea salt, and black pepper.
Toss the steak strips in the spice blend until evenly coated.
Heat the avocado oil in a large skillet over medium-high heat.
Add the sliced red bell pepper and red onion to the skillet, sautéing for 3-4 minutes until they begin to soften.
Push the vegetables to the side and add the seasoned steak, searing for 2-3 minutes until browned and cooked through.
Stir in the lime juice to deglaze the pan and coat the steak and vegetables.
Wipe the skillet clean or use a separate pan to toast the tortilla over medium heat.
Sprinkle the shredded cheddar cheese over half of the tortilla, top with the steak and pepper mixture, and fold the tortilla over.
Cook for 1-2 minutes per side until the tortilla is golden brown and the cheese is perfectly melted.