Mix together sugar, cake flour, baking powder, baking soda, and salt.
Add peanut butter and mix until combined.
Add eggs and peanut oil and mix until just combined.
Slowly add milk and mix on low speed until just combined.
Fill liners 2/3 full and bake for 14 minutes at 350 F. Check for doneness and cool.
For the frosting, beat butter on high, then add peanut butter, salt, and powdered sugar a bit at a time.
Frost and enjoy!