Preheat oven to 375°. In an ungreased 9-in. square baking pan, combine butter and brown sugar. Drain pineapple, reserving 1/3 cup juice. Arrange 9 pineapple slices in a single layer over sugar (refrigerate any remaining slices for another use). Sprinkle pecans over pineapple; set aside. , In a large bowl, beat egg yolks until thick and lemon-colored. Gradually add sugar, beating well. Blend in vanilla and reserved pineapple juice. Combine flour, baking powder and salt; add to batter, beating well. , In a small bowl with clean beaters, beat egg whites on high speed until stiff peaks form; fold into batter. Spoon into pan., Bake 30-35 minutes or until a toothpick inserted in center comes out clean. Let stand 10 minutes before inverting onto serving plate. Place a cherry in the center of each pineapple slice. If desired, serve with whipped topping.