Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition, and then stir in the vanilla extract.
In another bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Do not over-mix.
Fold in the creamy peanut butter until the mixture is smooth and well incorporated.
Spoon the batter into the lined cupcake pan, filling each cup about two-thirds full.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and allow to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
Once cooled, use a piping bag to inject jelly into the center of each cupcake.
Frost with additional peanut butter frosting or a drizzle of melted chocolate if desired.