Heat oven to 350°F. Line 18 standard-sized muffin tins with paper baking liners in red, white and blue colors, if desired.
In the bowl of an electric mixer, combine all the cake ingredients. Mix 2 minutes on medium speed until well combined and batter is smooth. Divide batter between cupcake liners. Bake 16 to 18 minutes or until a toothpick inserted in the center comes out clean. Cool in pan 5 minutes. Transfer cupcakes to a wire cooling rack and cool completely, about 30 minutes.
Meanwhile, prepare the frosting. In the bowl of an electric mixer, beat together the sour cream and butter until smooth. Add in the powdered sugar and vanilla and beat until well combined. Add 1 to 2 tablespoons milk to thin the frosting as needed.
Frost cooled cupcakes with frosting. Top with fresh blueberries. Store leftover cupcakes in the refrigerator loosely covered with plastic wrap.
Recipe by Espresso and Cream at http://espressoandcream.com/2014/06/4th-of-july-sour-cream-cupcakes.html