In small saucepan, combine raisins, water and bourbon.
Cover and bring to a boil over medium heat.
Remove from heat and let stand, covered, 10 minutes.
In medium bowl, cream butter; gradually add sugar, continuing to beat until light and fluffy.
Beat in egg.
In small bowl, sift flour with baking powder, baking soda and salt.
Add to creamed mixture alternately with raisin mixture.
Stir in walnuts.
Spoon into greased, waxed paper-lined, 9-inch square pan.
Bake in preheated 350°F oven 30 minutes or until pick inserted near center comes out clean.
Cool in pan 10 minutes.
Loosen edges; remove from pan.
Cool completely on wire rack.
Gently peel off paper.
Serve plain or topped with your favorite icing.