Mix together all the sauce ingredients in a small bowl until well combined. Refrigerate until ready to use.
Heat the oil in a large skillet over medium high heat. Add in the steak. Season it with salt and pepper. Sauté until the steak is cooked through. Remove from the heat. Let rest for 5 minutes. Then cut the steak into thin slices.
Preheat a large skillet or griddle over medium heat. Lay a tortilla on the griddle or skillet once heated.
Sprinkle 1/4 cup of each of the shredded cheeses and half of the American cheese slices onto half of the tortillas. Spread 1/4 of the steak mixture on top of the cheeses.
Spread approximately 1 tablespoon of the sauce onto the other side of the tortillas (without the cheese and steak).
Fold the tortilla in half. Cook until golden brown and the cheese starts to melt. Flip and cook until the other side is browned as well.
Remove from the skillet or griddle. Continue this process until all the quesadillas are made.
Then they are ready to slice, serve and enjoy!
Notes
These are best served fresh but you can refrigerate the leftovers in an airtight container for up to 3 days.