Preheat oven to 350°F. Grease and flour a 9 inch (10-cup) Bundt pan.
In a large bowl, beat the butter and sugar until light and fluffy, about 2-3 minutes.
3/4 cup (170g) salted butter, 1 3/4 cups (350g) granulated sugar
Add the eggs one at a time, beating well between each addition. Scrape down the bottom and sides of the bowl, then add in the sour cream and vanilla mixing until combined.
2 large eggs, 1 cup (240g) sour cream, 1 teaspoon pure vanilla extract
Add the flour, baking powder, and salt, mixing them into the batter just until blended in.
1 2/3 cups (234g) all-purpose flour, 1 teaspoon baking powder, 1/4 teaspoon salt
Gently fold in blueberries. If using frozen blueberries, no need to thaw. Just toss them with 1 tablespoon of flour first. The batter will be thick.
2 cups fresh or frozen blueberries
Generously spray a 10- or 12-cup bundt pan with baking spray or grease well with butter and dust with flour. Spoon half of the batter into the prepared pan.
In a separate bowl, stir together the brown sugar, cinnamon and chopped walnuts. Sprinkle the brown sugar mixture over the batter in the pan.
1/2 cup brown sugar, 1 teaspoon ground cinnamon, 3/4 cup chopped walnuts
Spoon the remaining batter on top of the brown sugar walnut layer, and smooth it out.
Bake for 55 to 70 minutes until a knife or long skewer inserted into the cake comes out clean with just a few crumbs.
Cool in the pan for 10 minutes, then invert the bundt pan onto a cake plate or other serving plate. The cake should come right out, but if not, tap the pan firmly a few times with the butt end of a knife to help loosen it. Let cool, then dust with powdered sugar just before serving. I like to serve this cake slightly warm, but it's delicious completely cooled as well.
Powdered sugar