Preheat oven to 350 degrees. Spray a 6 cup bundt pan with cooking spray.
Sift together flour, baking powder, baking soda and salt in a large bowl.
In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat together sugar, buttermilk, eggs and oil.
Add dry mixture in 3 stages. Mix until just moist. Do not over mix. This will result in a tough cake.
Toss all 4 cups of fresh berries in 1/4 cup sugar.
Gently fold 3 cups of berries into batter (reserving 1 cup.) Pour into the bundt pan. Sprinkle remaining berries on top and tap several times to get them to stick to the batter. The weight of the berries can cause them to sink to the top of the cake. By adding a layer on the bottom you will equally distribute throughout the cake.
Bake for 40-45 minutes, or until the top is lightly browned and it passes the toothpick test. Set on wire rack until fully cooled.
Combine powdered sugar, water and vanilla in a small bowl until a pourable consistency- not too watery, but not too thick. Pour over cooled bundt cake.
Best if served 1-2 days after baking.
If you've tried this recipe, come back and let us know how it was!
*You can use frozen berries, but make sure they are unsweetened and thawed to reduce excess water and liquid.