Preheat oven 350 F. Combine brown sugar, 1 tablesbpoon butter, raisins, boiling water and boil together for 5 minutes. Remove from heat and stir in vanilla; set aside. Cream butter and sugar. Sift flour and baking powder together and add alternately with milk to sugar ~butter mixture. Pour batter into a greased 9 x 13 in pan. Put hot syrup over batter, spreading raisins evenly. Bake 30 - 35 minutes in preheated 350 oven. When baked, the syrup and raisins will be at the bottom of the cake. This dessert may be served plain, or with whipped cream or vanilla ice cream.