Preheat oven to 350 degrees. Grease a 9x13-inch baking pan with nonstick baking spray.
In a mixing bowl, add in the melted butter, peanut butter, brown sugar, and flour. Mix with a hand mixer until crumbly. Set aside.
In a mixing bowl, add in the cooled melted butter and sugar. Beat with a hand mixer until incorporated.
Add in the egg and vanilla and beat until incorporated.
In a separate bowl, add in the baking soda, baking powder, and flour. Whisk until incorporated.
Add half of the flour into the wet mixture and mix until just combined.
Add all of the buttermilk. Beat on low until just combined.
Add in the remaining flour and beat until just combined.
Pour the batter into the prepared pan and even it out.
Spread the jelly and melted peanut butter on top of the batter.
Carefully spread all of the crumb on top of the peanut butter and jelly. Make sure all the cake is covered with crumbs.
Place the cake into the oven and bake for 1 hour or until the cake is done. Place a clean toothpick in the center of the cake. If there's batter, not melted peanut butter, on the toothpick, let it bake longer. If it comes out with moist crumbs or clean, it's done.