Preheat the oven to 375 degrees . On a floured surface, unroll the pastry; cut into 6 rectangles. Line a baking sheet with parchment; transfer the pastry to the sheet. Lay the plum slices evenly on the pastry. Brush the plums with the butter and sprinkle 1 tsp. sugar over each pastry.
Bake until golden, 25 to 30 minutes. Serve warm or at room termperature.