Set oven to 350˚F and line a 9x9 inch pan with parchment paper, and grease lightly.
In a medium mixing bowl, cream together the butter, peanut butter and brown sugar until fluffy.
Add egg and vanilla, and mix again.
Add flour, baking powder and baking soda. Mix gently on low speed, or fold in with a rubber scraper to incorporate until fully blended and smooth.
Fold the mixture, except for about ⅔ cup, into prepared pan and spread so that it reaches the sides evenly.
Spread jelly over entire base, then add the remaining dough randomly over the jelly.
Bake for 20 minutes, check. If it is browned nicely remove. If not, set for 5 more minutes and cover with foil so it will not brown too much. Remove and set on cooling rack.
Once cooled, use parchment to remove from pan to slice. Wipe knife with each.
Notes
Heat jelly for 20 seconds in the microwave if this is easier