Preheat your oven to 425°F to prepare for baking the quesadillas.

Lightly spray one of two 18×13-inch baking sheets with nonstick cooking spray to prevent sticking.

In a small bowl, combine the fajita seasoning with 3 tablespoons water, stirring until fully blended.

Heat 1½ tablespoons of vegetable oil in a 10 to 12 inch skillet over medium-high heat. Add the sliced onions and sauté for 2 to 3 minutes until they begin to turn opaque.

Add the sliced green bell peppers to the onions and continue to sauté for another 2 to 3 minutes until onions are translucent and peppers soften. Transfer the cooked veggies to a plate.

Return the skillet to heat and add the remaining 1½ tablespoons oil. Add the chicken strips and cook for 5 to 6 minutes until no longer pink, stirring often.

Pour the water and fajita seasoning mixture over the chicken in the skillet. Cook an additional 2 to 3 minutes until chicken is well coated and seasoned. Transfer to a heat-safe bowl or plate.

Place six tortillas around the edges of the sprayed baking sheet, overlapping and letting them hang halfway over the pan edges, leaving a gap in the center. Place one tortilla in the center bottom gap.

Slice the last tortilla in half using a sharp knife or pizza cutter.

Sprinkle 2 cups of shredded cheese evenly over the tortillas arranged on the pan.

Evenly spread the sautéed onions and bell peppers over the cheese layer.

Spread the cooked chicken strips over the vegetable layer.

Spread the rinsed and drained black beans over the chicken, then top with the remaining 2 cups shredded cheese. Sprinkle chopped cilantro over the top.

Starting from each side of the sheet pan, carefully and tightly fold the tortillas towards the middle. Dampen edges with water using a pastry brush if they don’t stick.

Dampen edges of each half tortilla and press them over the center of the quesadilla to seal.

Place the second baking sheet on top of the folded tortillas to keep edges together during baking. Optionally, add pie weights on top to hold in place.

Bake in the preheated oven for 20 minutes.

Remove the top baking sheet and bake for an additional 5 to 7 minutes until the quesadilla top turns golden brown.

Let the quesadilla rest for 2 to 3 minutes. Using a sharp knife or pizza cutter, cut into 3 slices by 4 slices. Serve hot with optional garnishes like sour cream, guacamole, and pico de gallo.