Preheat oven to 350 degrees. Spray an 8-inch cake pan with cooking spray.
In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt, whisking well to eliminate lumps. Make a well in the center of the dry ingredients and add the water, oil, 1 tablespoon vinegar, and 2 teaspoons vanilla. Whisk to combine. Pour into prepared pan and bake 25-30 minutes or until the edges are dry and have pulled bake from the sides of the pan and a toothpick inserted into the center of the cake comes out clean. Let cool in rack in the pan for 15 minutes the remove from pan and cool completely.
While the cake is baking, place the berries in a bowl, top with 1/3 cup vinegar, stir and let sit at room temperature. Stir occasionally.
When the cake is cooled, whip the cream with powdered sugar and 1½ teaspoons vanilla until soft peaks form.
Top the cooled cake with whipped cream, drain the berries, then place on top of the whipped cream.