Preheat your oven to 350°F (175°C).
In a mixing bowl, combine peanut butter and sugar until smooth.
Add eggs one at a time, beating well after each addition.
Gradually add milk, mixing until well combined.
In a separate bowl, whisk together flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Pour the batter into a greased cake pan.
Bake for 30 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool before serving.