Step 1: Season the steak: In a medium bowl, toss the thinly sliced steak with olive oil, chili powder, cumin, garlic powder, cayenne pepper (if using), salt, and black pepper. Let it marinate for at least 10 minutes, or up to 30 minutes at room temperature.
Step 2: Cook the steak: Heat a large cast-iron skillet or heavy-bottomed pan over medium-high heat. Add the seasoned steak in a single layer (cook in batches if necessary to avoid overcrowding). Cook for 2-3 minutes per side until browned and cooked to your desired doneness. Remove the steak from the pan and set aside.
Step 3: Prepare the tortillas: Reduce the heat to medium. Lightly butter or brush one side of a flour tortilla with olive oil. Place the tortilla, buttered/oiled side down, into the hot skillet.
Step 4: Assemble the quesadilla: Sprinkle about 1/4 cup of the shredded Monterey Jack cheese and 1/8 cup of the cheddar cheese over one half of the tortilla. Arrange a portion of the cooked steak over the cheese. Top the steak with another sprinkle of Monterey Jack and cheddar cheese.
Step 5: Fold and cook: Once the cheese on the bottom half starts to melt and the tortilla begins to brown lightly (about 1-2 minutes), carefully fold the empty half of the tortilla over the filled half. Press down gently with a spatula.
Step 6: Brown both sides: Cook for another 2-3 minutes on each side until both sides are golden brown and crispy, and the cheese is completely melted and gooey. Remove the quesadilla from the skillet.
Step 7: Repeat and serve: Repeat the process with the remaining tortillas, cheese, and steak. Slice each cooked steak quesadilla into wedges. Serve immediately with your favorite toppings such as sour cream, guacamole, salsa, or pico de gallo. Enjoy this delicious steak quesadilla recipe!