Preheat the oven to 350° and generously butter an 8x8 or 7x10 baking dish.
Dry Ingredients
In a medium bowl, whisk together the flour, sugar, baking soda, cinnamon, ginger and salt.
Stir the toasted walnuts into the dry ingredients.
Wet Ingredients
Cut the apple into quarters, remove the core, and grate the quarters on a box grater.
Mix the grated apple, oil, milk, egg, and vanilla in a large measuring cup or 4-cup bowl.
Combining
Pour the wet ingredients into the bowl containing the dry ingredients and use a rubber scraper or wide spoon to combine the two. Don't over-mix - this is going to be a rough batter.
Scrape the batter into the prepared pan, and place in the preheated oven. Bake for 20 to 25 minutes, until the top is nicely browned and a toothpick inserted near the center comes out with just a few moist crumbs.
Remove the cake from the oven and cool on a baking rack for at least 10 minutes before cutting.
This is very good warm, topped with powdered sugar, whipped cream, or maybe ice cream. It's pretty good plain too!
Notes
This cake should be refrigerated and can be gently reheated in the oven or a toaster oven. NOT in the microwave, which will make it mushy.*I linked to a set of glass measuring cups that are high quality and a good value. They're safe for hot liquids, the microwave, and highly shatter-resistant. Everybody needs a good set of glass measuring cups, right?