Sift flour, white sugar, soda, salt, baking powder and spices into a large mixing bowl. Mix in 125g butter or margarine, buttermilk and apple sauce. Beat for 2 minutes with an electric mixer on medium speed. Beat in eggs. Fold in 3/4 cup chopped nuts. Pour batter into a greased and floured 20x30cm pan.
Bake at 180 degrees C for 50 minutes.
Mix icing sugar, cream cheese and vanilla until smooth. Melt 65g butter over medium heat and add 1 cup chopped pecans. Keep stirring until browned. Stir cooled pecans into cream cheese mixture. Ice the cooled cake.