Preheat oven to 350 degrees F (175 degrees C). Grease and flour an 8 inch square baking pan.
In a medium bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla.
Combine the flour, baking powder, baking soda and salt; stir into the creamed mixture alternately with the buttermilk. Fold in the blackberries. Spread evenly into the prepared pan.
Bake for 40 to 50 minutes in the preheated oven. Cake is done when it springs back to the touch.
Meanwhile, combine the wine and sour cream in a small saucepan. Heat and stir until smooth. Remove from heat and set aside.
When cake is done, remove from oven and set aside to cool. Once cool, cut into squares and serve with a drizzle of the wine sauce.
Interesting Facts
Blackberries are high in antioxidants and vitamin C.
This cake is great for special occasions such as birthdays or anniversaries.
The wine sauce can be made ahead of time and refrigerated until ready to use.