Pineapple Upside Down Cake

1/2 c margarine, melted
1/2 c brown sugar
1 yellow cake mix (make according to directions-- except I use pineapple juice from drained pineapple for water)
1- 16 oz can of sliced pineapple
maraschino cherries

Pour melted margarine in 9x13 pan.   Sprinkle brown sugar over the top.   Drain pineapple slices (reserve juice for cake mix).   Place rings around bottom of pan.  You can add maraschino cherries inside the rings if desired.   Make yellow cake mix as per directions on box (using pineapple juice for water).   Pour cake batter evenly over top of pineapple.    Bake at 350 deg for 35-40 min., until cake is done.   Let cool about 5 minutes and then invert onto cookie sheet.