Lightly grease and lightly flour a 16" x 11" baking pan, while preheating the oven to 325 degrees F. In a mixing bowl, whip together the canna butter and sugar. In a separate bowl, separate the egg yolk from the egg white, with a spoon. Add the egg yolk to the flour/butter mixture, followed by flour, salt and cinnamon, all sifted. Mix well, before pouring into the prepared pan. Vigorously beat the egg white and spread on top of the batter. Then add the chopped walnuts to the top of the batter. Bake for roughly 30 minutes, or until a toothpick inserted in the center comes out clean.