Cream butter and sugar, add egg yolk and vanilla and mix well. Add flour, soda, cinnamon (sifted to- gether). In a l0 x 10 inch low sided pan, ungreased, pat dough evenly into pan until it is flat. Whip egg white until foamy. Pour over dough and spread. Cover it with nuts. Bake for 35 minutes at 350 degrees. Sprinkle with powdered sugar. Bake for another 5 minutes. Cut into strips while still hot.