THAW pastry sheet at room temperature 30 min. Preheat oven to 425° F.
UNFOLD pastry. Trim pastry to make 9" circle. Place on baking sheet. Bake 10 min. or until golden. Remove from baking sheet and cool on wire rack.
PEEL bananas. Cut in half lengthwise and then crosswise.
MIX 1/2 cup brown sugar, rum, butter, lemon juice and cinnamon in skillet. Heat to a boil. Cook and stir until mixture thickens, about 2 min. Add bananas and mix until coated.
MIX sour cream and remaining sugar. Spoon banana mixture over pastry.
TOP with sour cream mixture. Cut into wedges.