Slice the top sirloin steak into thin, bite-sized strips and thinly slice the red bell pepper and onion.
Season the steak strips evenly with the sea salt, black pepper, cumin, and chili powder.
Heat the olive oil in a large non-stick skillet over medium-high heat until shimmering.
Add the steak strips to the skillet and sear for 2-3 minutes until browned and cooked through, then remove from the pan and set aside.
In the same skillet, add the sliced peppers and onions, sautéing for 3-4 minutes until they are tender-crisp and slightly caramelized.
Wipe the skillet clean and place the whole wheat tortilla in the pan over medium heat.
Sprinkle half of the Monterey Jack cheese over one half of the tortilla, then layer on the seared steak and sautéed vegetables.
Top with the remaining cheese and fold the tortilla in half.
Cook for 2 minutes per side, pressing down gently with a spatula, until the tortilla is golden-brown and the cheese is completely melted.
Slice into wedges and serve immediately.