Dice your choice of beef, vegetables, or chicken into small pieces. Season generously with salt and pepper and let them marinate for about 10 minutes.

Heat a skillet over medium-high heat and add a drizzle of oil. Cook the filling until browned and cooked through, about 6-8 minutes for chicken or beef, or until veggies are tender.

On a large tortilla, spread a layer of cheese followed by your cooked filling. Add more cheese on top and place another tortilla on top.

Transfer the assembled quesadilla to the skillet over medium heat. Cook for 3-4 minutes on each side until golden brown and crispy, and the cheese is melted.

Remove from heat and allow to cool slightly before slicing into wedges. Serve warm with salsa, guacamole, or sour cream.