Preheat oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a medium bowl, combine peanut butter, pumpkin puree, egg, and applesauce. Stir until smooth and creamy.
Add oat flour and baking powder to the wet mixture. Stir slowly until a scoopable batter forms. Do not overmix.
Spoon batter into lined muffin tin, filling each cup about two-thirds full. Smooth tops lightly.
Bake for 18–22 minutes until firm on top and a toothpick inserted in the center comes out clean.
Remove cupcakes from pan and cool completely on a wire rack for at least 30 minutes.
Spread a small spoonful of plain Greek yogurt on each cooled cupcake. Top with a banana slice or small dog biscuit if desired.
Serve one cupcake as a treat. Store leftovers in the refrigerator for up to 5 days.