Preheat oven to 350˚F
In an 8x8" baking dish, combine ½ cup butter, the flour and powdered sugar together. Mix with a pastry blender or your fingers until crumbly.
Press evenly into the pan and bake for 5 minutes. Allow to cool on a cooling rack while preparing the topping.
In a medium bowl, combine brown sugar, ¼ cup butter, raisins, eggs, vinegar and vanilla. Mix together well.
Pour over prepared base and bake for 30 minutes.
Cool completely. Cut into 16 squares or 20 rectangular pieces.