In a medium-sized mixing bowl, combine flour, rolled oats, sugar, and brown sugar. Add in butter and work into the dry mixture using a fork until crumbly. Set aside.

Preheat the oven to 350°. Line the bottom and sides of a 9″ springform pan with parchment paper and lightly spray with baking spray. Set aside. In a large mixing bowl, combine cake flour, flour, baking powder, cinnamon, salt, and baking soda. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment, combine sugar and butter. Beat together on medium speed for 2 minutes until fluffy. Add in the eggs and mix to combine. Add in milk and vanilla and mix until incorporated.

Next, add in the flour mixture and mix until just combined. Once the flour mixture is added to the recipe, be sure to only mix until just combined. Overmixing can cause the gluten to overdevelop, resulting in a crumbly cake.

Transfer the batter to the prepared springform pan. Arrange the apples on top of the batter as evenly as possible, but this doesn’t have to be perfect.

Add the streusel on top, then place into the preheated oven on the center rack.

Bake for 1 hour or until baked through. Once baked, remove from the oven and place onto a wire cooling rack to cool.

Make a simple glaze for the finished cake by whisking together ½ c powdered sugar, 2 tsp of milk, and ½ tsp of vanilla. Add more milk for a thinner glaze or more powdered sugar for a thicker glaze.