Slice the flank steak into thin strips across the grain and season evenly with sea salt, black pepper, chili powder, and garlic powder.
Thinly slice the red bell pepper and yellow onion into long strips.
Heat half of the olive oil in a large non-stick skillet over medium-high heat until shimmering.
Add the steak strips to the skillet in a single layer and sear for 2-3 minutes until browned and cooked through, then remove and set aside.
Add the remaining oil to the same skillet and sauté the peppers and onions for 4-5 minutes until tender and slightly caramelized.
Wipe the skillet clean and place the whole wheat tortilla inside over medium heat.
Sprinkle half of the shredded cheddar cheese on one side of the tortilla, then layer on the seared steak and sautéed vegetables.
Top the filling with the remaining cheese and fold the tortilla in half to create a semi-circle.
Cook for 2 minutes per side, pressing down gently with a spatula, until the tortilla is golden brown and the cheese is completely melted.
Transfer to a cutting board, let rest for one minute, then slice into three wedges and serve.