Preheat oven to 400°F. Place dishes on a rimmed baking sheet. Smear bottom of each dish with 1 tablespoon butter. Sprinkle each evenly with 2 tablespoons sugar. Overlap slices from 1 banana over sugar, arranging in concentric circles to cover. Top each dish with 1 puff pastry round, tucking in edges of pastry.
Bake until pastry is golden and puffed and filling is bubbly, 20-25 minutes. Invert onto plates.
