Sauté the veggies: Heat ½ teaspoon olive oil in a small skillet over medium heat. Add the diced red bell pepper and onion. Cook for about 2 minutes, just until they begin to soften. Remove from heat and set aside.
½ teaspoon olive oil, ½ cup diced red bell pepper, ½ cup diced red onion
Mix the filling: In a large bowl, combine the shredded cheddar and Oaxaca cheese, chipotle chili powder, salt, roasted poblano pepper, cilantro, shredded chicken, and the sautéed vegetables. Toss everything together until well mixed.
6 oz sharp cheddar cheese, 6 oz oaxaca cheese or your favorite melting cheese such as monterrey, fontina, or mozzarella (see note), 1 cup shredded rotisserie chicken, ¼ teaspoon chipotle chili powder, 1 roasted poblano pepper, ¼ cup chopped cilantro, ½ teaspoon kosher or sea salt
Assemble the quesadillas: Heat a comal or cast iron skillet over medium-low heat and lightly coat it with olive oil spray. Working one at a time, spread about ½ cup of the chicken and cheese mixture over half of each tortilla, then fold it over to form a half-moon shape.
Cook until golden: Place two quesadillas on the skillet at a time and cook for about 2 minutes per side, or until the tortillas are golden brown and the cheese is melted. Transfer to a cutting board and slice in half. Repeat with the remaining tortillas. To keep them warm, place the cooked quesadillas in a 200°F oven while finishing the rest.
Serve: Serve the quesadillas hot with diced avocado, Mexican crema, pico de gallo, salsa, and a side of refried beans.