Preheat oven to 350 degrees F. Oil a bundt pan, cake pan, or 10-inch springform pan; sprinkle pan lightly with sugar.
In a large mixing bowl, whip the butter at medium speed until creamy. Reduce the speed to low and gradually add the sugar, mixing well. Add the eggs, one at a time, mixing well, and then add the sour cream and vanilla extract. Increase the speed to medium and mix well, scraping down the sides of the bowl as needed.
In another large bowl, combine the flour, baking powder, cinnamon, and salt; mix thoroughly. Add the flour mixture to the butter mixture in several increments, mixing well after each addition. Gently stir in the pecans or walnuts and berries.
Pour the batter into the prepared pan and bake for approximately 40 to 50 minutes, or until a toothpick inserted in the center comes out clean.
Makes 1 cake.
* If fresh blackberries are not in season, you can substitute other fresh berries, such as blueberries or huckleberries, or use dried fruits such as raisins, currants, or dried cherries.
Blackberry Coffee Cake with Sour Cream Recipe: https://whatscookingamerica.net/cake/blackberrycoffeecake.htm