Preheat the oven to 350°F and lightly grease a 6-cavity mini Bundt pan with a small amount of coconut oil.

In a medium bowl, whisk together the oat flour, brown rice flour, baking powder, and baking soda until well combined and no clumps remain.

In a separate large bowl, add the peanut butter, unsweetened applesauce, coconut milk, melted coconut oil, and egg, then whisk until the mixture is smooth and well blended.

Gradually add the dry ingredients to the wet ingredients, stirring with a spatula or wooden spoon just until a thick, smooth batter forms.

If the batter is too thick to scoop easily, stir in an extra tablespoon of coconut milk at a time until it is thick but pourable.

Divide the batter evenly among the prepared mini Bundt cavities, filling each about 3/4 full.

Tap the pan gently on the counter to release any air bubbles and level the batter.

Bake for 18 to 20 minutes, or until the cakes are set and a toothpick inserted into the thickest part comes out clean.

Let the pan cool on a wire rack for 10 minutes, then carefully remove the mini Bundt cakes and allow them to cool completely on the rack before serving to your dog.