Preheat oven to 350° F. Line the inside of an 8 ½ by 4 ½ inch loaf pan with nonstick foil or line with regular foil and grease with butter/coconut oil or nonstick spray.
In a medium bowl, whisk together flour, baking powder, spices, and salt. Set aside.
In a mixing bowl, using an electric mixer, beat the whole egg and the white for a minute. With the mixer on high speed, gradually add sugars and beat for another 2 minutes or until pale and bubbly. Beat in the vanilla.
Add the flour mixture to the egg mixture and stir with a heavy-duty scraper until blended, then fold in the walnuts and apple.
Spread apple mixture in the loaf pan. Dampen fingers with a little water and press lightly to even out the top. Sprinkle with cinnamon sugar if desired. Bake for 30 minutes.
Remove from oven and let cool, then remove from loaf pan and refrigerate until very firm. You can also freeze, but if you freeze it don’t freeze it solid or it will be too hard. The goal is to get it very firm so that you can make thin slices.
When the loaf is cold and firm, cut very thin slices of the apple loaf (you can use a serrated knife or a very sharp chef’s knife) and lay them on a baking sheet. Bake at 250 for about 30-40 minutes or until edges are brown and crisp. I recommend checking after 30 minutes, then removing any super thin ones that seem done and letting the remaining bake for another 10. You should get about 30 total.