Prepare the Filling

1. Preheat Oven: Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper or lightly grease it with cooking spray.
2. Season the Chicken: If you’re using chicken, shred it and place it in a mixing bowl. Add the chili powder, cumin, garlic powder, salt, and pepper. Toss to coat the chicken evenly in the spices.
3. Prepare Veggies: Dice the bell peppers, red onion, and any other veggies you want to add (like zucchini or mushrooms). If using black beans, drain and rinse them.
4. Mix the Filling: In a large bowl, combine the shredded chicken (or other protein), bell peppers, red onion, black beans, and cilantro. Stir until the ingredients are well distributed.

Assemble the Quesadillas

1. Layer the First Tortilla: Lay a tortilla flat on the sheet pan. Brush with a little olive oil or melted butter.
2. Add the Filling: Spread a generous amount of the chicken and veggie mixture over the tortilla.
3. Add Cheese: Sprinkle an even layer of shredded cheese over the filling.
4. Top with Another Tortilla: Place another tortilla on top, pressing it down gently to secure the filling inside.
5. Repeat the Process: Repeat the layering process until all six tortillas are stacked. Brush the top tortilla with a little more olive oil or melted butter.
6. Bake the Quesadilla Stack: Place the sheet pan in the oven and bake for 15-20 minutes, or until the tortillas are golden brown and crispy, and the cheese is melted.

Slice and Serve

1. Slice into Squares: Once the quesadillas are done, remove them from the oven and let them cool for a minute. Slice them into squares or wedges using a sharp knife or pizza cutter.
2. Top and Serve: Serve with your favorite toppings like sour cream, guacamole, salsa, or a squeeze of lime.