1cupwhole wheat pastry flour,or all-purpose; I do NOT recommend regular whole wheat
jelly or jam of your choice
Preheat oven to 350 degrees.
Cream butter and peanut butter in the bowl of an electric mixer. Add sugar and beat until fluffy. Add egg and vanilla and beat until incorporated. Stir in flour, baking powder and salt with the mixer on low speed. Make sure to scrape down the sides of the bowl occasionally. Add milk and mix until batter comes together.
Butter and flour an 8×8 cake pan. Pour in batter, then add jelly to the top of the batter either with a pastry tip of with a spoon. Run a knife through the jelly to create swirls. It doesn’t have to look perfect – add as little or as much as you’d like. More jelly will keep the cake moist. Bake at 350 for 20-25 minutes or until cake is set. Let cool completely.