In a mixing bowl, combine the shredded chicken with chili powder, cumin, garlic powder, salt, and pepper. Toss well until the chicken is evenly coated with the spices. Set the seasoned chicken aside while you prepare the vegetables.

Dice the bell pepper and finely chop the red onion into uniform pieces for even cooking.

Take a flour tortilla and lay it flat on a clean surface. Sprinkle half of the Mexican cheese blend on one half of the tortilla, followed by a layer of seasoned chicken and diced vegetables. Top it off with the remaining cheese.

Heat olive oil or butter in a large skillet over medium heat. Place the quesadilla in the skillet. Cook for 3-4 minutes until the bottom is golden brown and crispy. Flip the quesadilla gently and cook for an additional 3-4 minutes until the cheese is melted.

Transfer the cooked quesadilla onto a cutting board and let it rest for 2-3 minutes. After resting, use a sharp knife or pizza cutter to cut the quesadilla into wedges for serving.