Step 1: Prepare Pan & Oven
Preheat oven to 175°C (350°F).
Grease and line a 6-inch round cake pan.
Step 2: Mix Dry Ingredients
In a medium bowl, whisk together flour and baking soda.
Step 3: Mix Wet Ingredients
In another bowl, beat peanut butter, applesauce, oil, and egg until smooth.
Stir in water.
Step 4: Make the Batter
Add dry ingredients to wet, stirring until just combined (thick but spreadable).
Step 5: Bake
Pour batter into pan, smooth the top.
Bake 25–30 minutes, until a toothpick comes out clean.
Cool completely.
Step 6: Frost & Serve
Mix yogurt and peanut butter until smooth.
Spread over cooled cake.
Decorate with dog treats if desired.