Prep the chicken filling: In a bowl, mix chicken, black beans, bell pepper, red onion, and spinach. Add Greek yogurt, salsa, cumin, chili powder, smoked paprika, garlic powder, a squeeze of lime juice, and a pinch of lime zest.
Season with salt and pepper. Stir until evenly coated.
Warm the skillet: Place a large nonstick skillet over medium heat. Add a light brush or spray of oil to coat the surface.
Assemble the first quesadilla: Lay one tortilla on a cutting board.
Sprinkle 2–3 tablespoons of cheese on half of it. Spoon a generous layer of the chicken mixture over the cheese. Top with another 2–3 tablespoons of cheese.
Fold the tortilla in half to form a half-moon.
Cook until golden: Transfer the folded tortilla to the hot skillet. Cook 2–3 minutes per side, pressing gently with a spatula, until the tortilla is crispy and the cheese has melted. Adjust heat as needed to avoid burning.
Repeat: Assemble and cook the remaining tortillas the same way, adding a touch more oil if the pan looks dry.
Rest and slice: Let each quesadilla rest for 1 minute on a cutting board.
Slice into wedges. This helps the cheese set and prevents the filling from spilling out.
Serve: Plate with extra salsa, a spoon of Greek yogurt or a light guacamole, fresh cilantro, and lime wedges. Add hot sauce or jalapeños if you like more heat.