Prepare produce: slice the bell pepper and onion into thin strips (cut the onion lengthwise). Chop the cilantro and set aside; prepare sour cream and guacamole if needed.
Heat 1 tablespoon olive oil in a skillet over medium-high heat.
Add the sliced pepper and onion and sauté, stirring often, until tender-crisp, about 3–5 minutes.
Stir in the shredded chicken, garlic powder, cumin, chipotle chili powder, salt, pepper, and lime juice. Mix until combined, then remove from heat and set aside.
Heat a second skillet over medium heat and add 1 teaspoon olive oil.
Place one tortilla in the hot skillet. Sprinkle half the grated cheddar evenly over the tortilla.
Top the cheese with the chicken and vegetable mixture, sprinkle with chopped cilantro, then add the remaining cheese.
Place the second tortilla on top and press down gently. Cook until the bottom tortilla is browned and the cheese begins to melt, about 2–3 minutes.
Carefully flip the quesadilla with a spatula and cook the other side until browned and the cheese is fully melted, about 2–3 minutes more.
Transfer the quesadilla to a plate, cut into quarters, and serve immediately with sour cream and guacamole.