Preheat oven to 350F.

Grease and flour an 8X8 baking pan.

In a saucepan, melt butter and stir in brown sugar until dissolved. Allow to cool slightly.

Pour butter and sugar mixture into a mixing bowl and add egg and vanilla. Mix well.

Sift flour into bowl and add baking powder and salt. Mix well.

Stir in walnuts.

Pour mixture into the prepared baking dish and bake for 25 minutes.

Remove from oven and allow to cool.

Dust with powdered sugar, cut into bars and serve.