Season the steak with salt and pepper.
In a skillet, heat olive oil and add the seasoned steak.
Once cooked though and well-browned on both sides, remove from pan and allow to cool before slicing.
In same pan, add the onions and cook, stirring occasionally, until tender and golden, about 4-6 minutes.
Remove from pan.
In same pan, lay one tortilla flat into the pan.
Sprinkle with 1/2 of the cheese, followed by the steak and onions.
Then, top with additional cheese and other tortilla.
Cook 2-3 minutes to allow the cheese to melt and the tortilla to cook.
Carefully flip the tortilla over and repeat until cheese is fully melted.
Remove from pan and slice into quarters before serving.
Top with sliced green onions.