Heat a large, heavy skillet (cast iron works best) over medium high heat, once hot, add a drizzle of oil to bottom of the pan and add about ⅓ of the steak, be sure not to crowd the pan or the steak will not brown. Leave undisturbed for 1 minute, then flip and cook another 1-2 minutes until almost cooked through, remove to a clean plate. Continue in batches until all steak is cooked.

Reduce heat to medium and add the onion and green pepper, and a small drizzle of oil if needed. Cook until veggies are tender, about 5-8 minutes, add a splash of water if they begin to stick at the end of cooking. Let the pan cool, then clean it out, or proceed with the recipe with another large pan.

Brush one side of each tortilla with oil. Heat a large skillet over medium low heat. Add two tortilla to the pan oil side down. Add a handful of cheese, steak, and veggies to each tortilla, push the top of the tortilla down onto the filling. Cook for about 2-4 minutes, or until tortilla is golden brown. Carefully flip and brown the other side for 2-4 minutes uncovered. If it browns too quickly before the cheese melts, turn the heat down to low. Repeat with remaining tortillas.

Slice the quesadillas in half. Serve immediately with a bowl of the vinaigrette and a dollop of sour cream in the bowl of vinaigrette.