1. Heat oven to 350℉.
2. Grease a 9-by-13-inch pan.
3. Beat butter and sugar in a large bowl until fluffy, about 2 minutes. Add eggs and peanut butter; beat until combined, about 2 minutes.
4. Whisk together salt, baking powder, and flour. Add to bowl of mixer; combine. Add vanilla.
5. Transfer two-thirds of mixture to prepared pan; spread evenly. Spread jam on top of peanut-butter mixture. Dollop remaining third of peanut-butter mixture on top of jam.
6. Sprinkle with peanuts.
7. Bake until golden, about 45 minutes.
8. Cut into 36 bars.