Preheat oven to 375°F degrees.
Line jelly roll pan with parchment paper.
Mix flour, cocoa, baking powder, and salt.
Beat eggs and sugar until thick and pale.
Add water and vanilla to egg mixture.
Fold dry ingredients into wet ingredients gently.
Spread batter evenly in prepared pan.
Bake for 12-15 minutes until springs back.
Turn cake onto powdered sugar-dusted towel immediately.
Roll cake in towel while still warm.
Cool completely on wire rack for 30 minutes.
Beat peanut butter, powdered sugar, and butter.
Add vanilla and cream to filling mixture.
Unroll cooled cake carefully and spread filling.
Roll cake again without towel this time.
Wrap in plastic wrap and refrigerate overnight.