Preheat oven to 350º. Grease and flour an 8-inch square baking dish. Mix together butter, sugar, apple sauce, eggs and vanilla. Combine flour, cocoa, baking powder and baking soda in medium bowl. Add the apple sauce mixture; stir to combine. Optional: Stir in pecans. Pour the batter into the prepared baking dish and bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Cool in the pan. Slice into squares.