Preheat oven to 350 degree f First make caramel and pour into the baking pan. Then arrange the pineapple slices over the caramel syrup . Sift together flour, baking powder and salt. Set aside. Cream the butter with the sugar until the mixture is light and fluffy. Add the eggs, one at a time, beating well after each addition. Stir in the vanilla..Add the flour mixture in three parts alternately with the pineapple juice, beginning and ending with the flour mixture. Beat well after each addition. Spread the batter evenly into the prepared pan.. Bake cake for 45 to 55 minutes, or until a tester comes out clean. Immediately invert the cake onto a plate.