Preheat your oven to 350 degrees.

In a large mixing bowl, combine the softened butter, applesauce, eggs, sugar, and vanilla extract. Mix until smooth.

Next, add in the almond flour, oat flour, baking powder, and salt. Stir until everything is well combined.

In a small bowl, combine the melted butter, oat flour, white sugar, and cinnamon evenly to create the cinnamon sugar filling.

For the crumble topping, add the brown sugar, almond flour, oat flour, and cinnamon to the room temperature butter. Use your hands or a fork to create crumbles. Set aside.

Grease or line an 8x8 baking dish. Pour half of the cake batter into the dish and spread it evenly.

Add half of the cinnamon sugar filling on top and gently swirl it into the batter.

Add the remaining batter and spread evenly again, then top with the rest of the cinnamon sugar filling. Swirl again.

Bake for 25 minutes.

Remove from the oven and gently place the crumble topping on top, pressing it slightly into the cake, especially in the middle.

Bake for another 18 minutes.

Take it out of the oven, let it cool completely, then cut into squares.

Enjoy!