
Preheat oven to 450 degrees
Combine chicken, cheese, beans, tomatoes, Greek yogurt, scallion whites, ¼ cup cilantro, chili powder, cumin, lime juice, and season filling with salt and pepper to taste.
Brush baking sheet with 1 Tablespoon butter.
Arrange two tortillas along one long side of baking sheet, with half hanging over the rim; repeat on the other side. Arrange one tortilla at each end, overhanging, then place one tortilla in center of baking sheet to cover bottom.
Spread filling over tortillas. Place remaining tortilla in center on top of filling, then fold overhanging tortillas to completely encase filling, pressing down firmly. Brush tops of tortillas with remaining 1 Tbsp. butter.
Bake quesadillas until tortillas are crispy and filling is hot and melty, about 20 minutes.
Cut quesadillas into squares; top with garnishes.