Melt butter in heavy skillet or around baking dish. Sprinkle brown sugar over butter. Drain pineapple slices, reserving liquid and arrange to attractive pattern on sugar and butter coating. Beat in sukgar until thick. Beat in, all at once, pineapple juice and Vanilla. Sift together dry ingredients and beat in at once. Pour baaatter over prepared fruit and bake in 350 degree oven for 30-35 minutes, or until a toothpick comes oust clean. Immeadiaately turn upside dowfn on serving plate. Djo not remove pan for a few minutes so sugar mixture can rsun down over the cake. Serve warm with either plain or whipped cream.