Preheat the oven to 350 degrees F. Grease and line two 6 inch cake pans with parchment paper.
In a medium bowl, whisk together the pumpkin, peanut butter, and coconut oil. Then whisk in the eggs.
Next, whisk in the oat flour and baking soda.
Pour the batter into the two prepared pans and bake for about 24-28 minutes or until a toothpick inserted comes out clean.
Allow cakes to cool completely before frosting.
For the Frosting:
Using an electric hand mixer, whip the peanut butter until light and fluffy.
Add peanut butter frosting to each layer.
Notes
I used Skippy peanut butter, but I'm sure just about any thick and creamy peanut butter will work.
To make your own oat flour, simply grind up rolled oats or quick cooking oats in a blender until it resembles flour.
Whipping the peanut butter is completely optional for the frosting, but it fluffs it up a bit and makes it look more like frosting.
Obviously your dog should not eat more than a slice of the cake at a time, so to store leftovers cut the cake up into individual slices, place in a zip lock bag, and freeze.