Preheat the oven to 350℉/180℃. For easy removal of the cake, place parchment paper on the bottom and 2 sides of the pan. Gently grease the two sides without parchment paper and then set aside.
In a medium sized bowl, add in flour, rolled oats, cornstarch, cinnamon, cloves, allspice, nutmeg, baking powder, baking soda, and salt. Stir to combine and set aside.
In a large bowl, add oil, brown sugar, eggs, vanilla, and applesauce. Whisk for 2-3 minutes until it's well combined. Make sure to scrap the sides of the bowl.
Mix in the dry ingredients and using a spatula, gently fold until a batter forms. Do not over-mix!
Slice the apples into small cubes and gently toss in ¼ tsp of cinnamon until evenly coated. Then add into the bowl. Gently mix until JUST combined, don't over-mix!
Spread the batter into the prepared pan evenly. In a small cup, add white sugar and cinnamon and mix together. Then sprinkle on top evenly. This will give you a sweet crunchy top.
Bake for 40-50 minutes, depending on your oven. It took me 48 minutes exactly. Allow it to cool, slice, and enjoy!
This cake is best enjoyed fresh day of and next day. Store in an airtight container for 3 days on your counter, or up to a week in the fridge.
