Preheat oven to 350 degrees F and grease and flour three 8 inch cake pans. (You can also use two 9 inch cake pans--batter shouldn't exceed ⅔ full)
In a separate bowl whisk the all purpose flour, baking powder, and salt to combine, set aside for later.
Cream the butter with the paddle attachment in your mixer, gradually add the sugar and beat until light and fluffy 3 to 5 minutes.
Add the eggs one at a time blending after each to incorporate.
In a small bowl or measuring cup, add the sour cream, milk, and vanilla extract.
While mixing on low speed, add the flour mixture alternately with the sour cream mixture to the butter, sugar, & egg mixture. Begin and end with the dry ingredients. (I add the flour mixture three times and the sour cream mixture twice). Mix just until incorporated.
Fold in the blueberries. Divide the batter between the three cake pans.
Bake at 350℉ for 20-25 minutes or until an inserted toothpick comes out clean or with just a few moist crumbs attached (or the centers of the layers spring back when lightly touched). Bake times may vary!
This recipe makes approximately 8-8.5 cups of batter.