Heat the oven to 350°.
Grease a 9x5" loaf pan with the olive oil (use your fingers or a pastry brush).
In a large bowl, whisk the almond flour, arrowroot, cinnamon, salt, baking soda and nutmeg.
Add the eggs, applesauce, ¼ cup olive oil and vanilla and whisk until combined (it won't be perfectly smooth but there shouldn't be any lumps of almond flour).
Peel, core and dice the apple. (Don't do this before you mix the other ingredients or the apple might brown before you can mix it in.) You should end up with about 1 cup, but a little less is fine. If you have more than 1 cup, lucky you! You can snack on the extra.
Fold the apple into the batter. Scrape the batter into the greased loaf pan and sprinkle the walnuts on top, gently pressing them down into the batter. Bake for 30-35 minutes, or until a toothpick inserted in the center of the loaf comes out clean.
Let the bread cool completely before slicing. Drizzle over the maple glaze, if using.