Preheat oven to 350 degrees. Grease a 12-cup or larger bundt pan.
In the bowl of a standing mixer, or by hand using an electric mixer on medium speed, mix together the apples, egg, and vegetable oil. Add flour, granulated sugar, baking soda, and ground cinnamon, and beat until well combined.
Pour batter into prepared bundt pan and bake until a toothpick inserted into the center of the cake comes out clean, about 50-60 minutes. Allow to cool 10 minutes in pan, and turn out cake onto a cooling rack.
To make the glaze, in a small bowl whisk together powdered sugar, water, and vanilla. Drizzle over cooled cake.
Apples: A wide variety of apple styles work well in baking, especially easy cake recipes like this. I love to mix two or three varieties to offer sweet and tart flavors, but feel free to stick with just one style if you like. Jonagold, Granny Smith, Honeycrisp, Gala, Fuji, Jazz, and Braeburns are among my favorites for this Cinnamon Apple Cake. (Here's a refresher on how to cut and core apples.)
Yield: This Apple Cinnamon Cake recipe makes one bundt cake which can generally serve between 12 to 20 depending on the thickness of your slices. At my home, this usually serves about 16 nice slices.
Storage: Cover any extra cake in plastic wrap and store covered at room temperature for up to 4 days.
Freezer: The unglazed cake can be cooled, wrapped tightly in a double layer of plastic wrap, and frozen for up to 3 months. Thaw overnight at room temperature.