Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x9 inch pan. Combine the flour, baking soda and baking powder; set aside.
In a medium bowl, cream together the sugar, butter and eggs until smooth. Add the flour mixture and beat until smooth. Finally, stir in the sour cream and vanilla. In a separate bowl, combine the nuts, confectioners' sugar and cinnamon.
Spread half of the batter into the 9x9 inch pan. Sprinkle a layer of the nut mixture, then spread the remaining batter and top with the rest of the nut mixture. Spread the melted butter over the top.
Bake for 1 hour in the preheated oven, until cake springs back to the touch.