Melt butter in a saucepan and add the brown sugar. Cook over low hear until well blended. Remove from heat and set aside.
Drain the juice from the pineapple rings and save the juice, then set aside.
Cream the butter and sugar, beat till fluffy. Add slightly beaten egg yolk and beat mixture. Sift cake flour and baking powder together, add in 2 increments with the pineapple juice to the mixture, then add vanilla.
Beat egg white until stiff peaks form, and fold into the cake batter.
Prep cupcake pan with paper liners, and put one pineapple ring in each cup. Put half of the melted sugar mixture evenly in each cup. Pour cake batter evenly in each cup 2/3 full. Then evenly pour the remaining sugar mixture on top.
Bake at 350 degrees for 25 minutes. Remove from oven to cool. Turn cupcakes over on a cake plate and top with a maraschino cherry.