Melt 1/2 stick butter in sauce pan. Add 2/3 cup brown sugar. Pour into 9 inch by 13 inch cake pan. Place pineapple slices on mixture. Prepare yellow cake mix according to package directions. Pour over pineapples. Bake according to cake mix directions. Invert on platter to serve.
Additional images of Denny Duback's Pineapple Upside Down Cake can be found here.
