Preheat the oven to 350F. In a large bowl, combine the flour, sugar, baking powder, and salt. Cut in the peanut butter with an electric beater on medium speed, until well combined. Add the egg and milk; stir until well blended. Spread half the batter into a 9" x 5" loaf pan that has been coated with nonstick cooking spray and spoon the preserves down the center of the batter. Top with the remaing batter, covering the preserves completely. Bake for 55 to 60 minutes, or until a wooden toothpick inserted in the center comes out clean. Invert onto a wire rack and let cool completely. Slice and serve.