Add shredded apples, cinnamon, vanilla extract, cocoa powder, oil, baking soda and apple cider vinegar to a large mixing bowl.
Mix thoroughly until well combined with apples. Mix in eggs.
Pour mixture/dough into 9x9 square glass pan lined with parchment paper. Top with 2 tbsp chocolate chips (optional). Bake for 45 minutes.
After 45 minutes, make sure it's cooked all the way through by inserting a toothpick or fork into the cake. If the toothpick comes out clean, it's done. If not, continue baking for 5 minute increments until toothpick comes out clean.
When the cake is done, let sit on counter to cool for 5-10 minutes.
Sprinkle some powdered sugar on top (optional) and eat up!
Notes
This recipe is not very sweet, so if you're looking for something a little more indulgent, I recommend adding 2-3 tablespoons of honey to the ingredients.