1-Preheat your oven to 350 degrees F: Preheat your oven to 350 degrees F. Spray a 10-inch spring-form pan with non-stick spray.
2-In a large bowl, mix together the: In a large bowl, mix together the flour, baking powder, baking soda, brown sugar, and salt. To this mixture, add the oil, buttermilk, eggs, and vanilla. Stir just until everything is well blended.
3-Pour the batter into the sprayed pan: Pour the batter into the sprayed pan. Top with the berries.
4-For the crumble, in a medium bowl: For the crumble, in a medium bowl combine the flour, brown sugar, and butter. Using your fingers (I think this just works best), mix and mash the ingredients together until a crumbly streusel forms. Sprinkle this streusel over the berries in the pan.
5-Bake the cake for 40 to 45: Bake the cake for 40 to 45 minutes, or until lightly golden brown on top and set. Allow the cake to cool almost all the way before removing it from the pan. Enjoy!