Step 1

In a medium skillet over medium-high heat, heat the oil until it shimmers. Add the onion, bell pepper, cumin, salt and black pepper and cook, stirring occasionally, until the vegetables soften and are charred in spots, about 10 minutes. Transfer to a bowl, add the chicken, barbecue sauce and jalapeños, if using, and stir to combine.

Step 2

Reduce the heat to medium. For each quesadilla, add 1 tortilla to the same skillet you cooked the vegetables in and sprinkle about 1/3 cup cheese evenly over top. Spread about 1/3 cup of the chicken mixture over half of the tortilla and cook until the cheese is melted and the tortilla starts to crisp on the bottom, about 4 minutes. Fold the tortilla in half over the filling and transfer it to a plate or platter. Repeat with the remaining tortillas, cheese and filling. (If the skillet ever gets dry, brush with a thin layer of oil.) Cut each quesadilla in half, if desired, and serve with sour cream and/or guacamole for dipping.