Melt the peanut butter and butter for 1 minute in a microwave-safe bowl. Blend together well then swirl into brownie batter. Swirl 1/3 cup of jam in a different direction with a butter knife, through the peanut butter, trying not to touch the sides of the pan as the jam will burn. Bake for 33-36 minutes until a tooth pick comes out clean when inserted into a middle brownie section. Let cool (brownies are gooey), then cut and serve.