Use parchment paper to line a 9x5x3-inch loaf pan. Lightly spray the lining with nonstick cooking spray.
Add the flour, baking powder, baking soda and salt to a large mixing bowl. Whisk to evenly combine.
In the bowl of a stand mixer, beat together the eggs, banana, sugar, peanut butter and vegetable oil.
Slowly pour the flour mixture into the mixing bowl, beating just until evenly combined with the wet ingredients.
Use a spatula to fold in the peanuts.
Pour half of the batter into the prepared loaf pan. Using a quarter cup of the jelly/jam, dollop it out over the surface of the batter. Use a butter knife to swirl it, not mix, into the batter.
Pour the remaining batter evenly out over top. Dollop another quarter cup of the jelly/jam evenly out over top, again using a butter knife to swirl it into the batter.
Bake at 350 degrees for 60-70 minutes. The loaf's done when a butter knife, inserted into the center, comes out clean. Remove form the oven.
Let the hot loaf 'rest' on a cutting board, or other safe surface for five minutes. Lift it out by the parchment paper, transferring to a wire rack to cool completely.
Heat the remaining 2 tablespoons of jelly/jam in a skillet over low heat, just until melted. Drizzle the preserves out over top of the cooled banana bread. Let sit for 60 seconds before slicing and serving.
While pb & j traditionally includes grape jelly, pictured here is blueberry jam. We've also had equal success with raspberry and strawberry. Pick your favorite and go with it.