Preheat the oven to 350°F and grease an 8x8-inch baking pan. I also line mine with a sheet of parchment paper.

In a large bowl, combine the applesauce, sugar, oil, almond milk, eggs, vanilla, and vinegar and whisk until combined.

In a medium bowl, whisk together the all-purpose, whole wheat, and almond flours, apple pie spice, baking powder, salt, and baking soda.

Add the dry ingredients to the bowl with the wet ingredients and stir until just combined, then fold in the walnuts. Pour into the prepared pan.

Bake for 32 to 39 minutes or until a toothpick inserted in the middle comes out clean. Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. When the cake is completely cool, top it with cream cheese frosting, if desired.