In a large mixing bowl, whisk together the oat milk and apple cider vinegar. Let sit for about 1 minute until the milk begins to curdle and separate to create a vegan buttermilk.
Next, add in the applesauce, olive oil, cane sugar, brown sugar, and vanilla. Whisk with the vegan buttermilk until smooth.
Once the wet ingredients are mixed, add the dry ingredients to the mixing bowl starting with the flour and adding the baking powder, baking soda, cinnamon, and salt on top. Then, use a whisk or spatula to GENTLY mix the batter just until all streaks of flour are gone. A lumpy batter is okay at this point!
Add in the diced apples and gently fold them into the batter. This step is best done with a spatula.