Using applesauce makes this coffee cake recipe lower in fat, plus it's a great way to use fresh blackberries when in season (or frozen when they're not).
Preheat the oven to 375 degrees. In a large bowl, combine the first 6 ingredients. In another large bowl, combine the egg, buttermilk, oil, applesauce, and vanilla. Stir into dry ingredients just until moistened. Fold in blackberries. Transfer to a 13-by-9-inch baking pan coated with cooking spray.
Bake for 35-40 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack.