01 - In a medium bowl, toss the chicken cubes with cumin, chili powder, smoked paprika, garlic powder, salt, and black pepper until evenly coated.
02 - Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Add the chicken and cook for 5-6 minutes until cooked through and lightly browned. Remove the chicken and set aside.
03 - In the same skillet, add the remaining olive oil. Sauté the red bell pepper and red onion for 3-4 minutes until softened. Add the chicken back in and stir to combine. Remove from heat.
04 - Place a tortilla on a clean work surface. Sprinkle one-quarter of the cheddar and Monterey Jack cheeses over half the tortilla. Top with one-quarter of the chicken and vegetable mixture. Fold the tortilla in half to cover the filling. Repeat with remaining tortillas and fillings.
05 - Melt 1/2 tablespoon butter in a clean skillet over medium heat. Cook each quesadilla for 2-3 minutes per side, pressing gently, until golden brown and cheese is melted. Add more butter as needed.
06 - While quesadillas cook, prepare the guacamole: In a bowl, mash the avocados with lime juice until mostly smooth. Stir in tomato, red onion, cilantro, salt, pepper, and jalapeño (if using).
07 - Slice the quesadillas into wedges and serve hot with guacamole on the side.