Let egg whites stand at room temperature for 30 minutes. Coat a 1-1/2-qt. souffle dish with cooking spray; set aside., In a small saucepan over medium heat, melt butter. Stir in the bananas, sugar and cornstarch until blended. Bring to a boil, stirring constantly. Cook and stir 1-2 minutes longer or until thickened. Transfer to a large bowl; stir in lemon juice, rum and lemon zest., Stir a small amount of hot mixture into egg yolks; return all to the bowl, stirring constantly. Allow to cool slightly., In a large bowl with clean beaters, beat egg whites until stiff peaks form. With a spatula, stir a fourth of the egg whites into banana mixture until no white streaks remain. Fold in remaining egg whites until combined. Transfer to prepared dish., Bake at 350° for 25-30 minutes or until the top is puffed and center appears set. Serve immediately.