Prepare the Cupcakes:

1. Preheat oven to 350°F (175°C) and line a cupcake tin with paper liners.
2. In a bowl, whisk together flour, baking powder, and salt. Set aside.
3. In a separate bowl, cream butter and sugar until light and fluffy.
4. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
5. Alternate adding the flour mixture and milk to the butter mixture, beginning and ending with flour. Mix until just combined.
6. Gently fold in blueberries to evenly distribute.
7. Divide batter evenly among cupcake liners.
8. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely.

Prepare the Blueberry Buttercream:

1. Beat butter until smooth. Gradually add powdered sugar and mix until combined.
2. Mix in blueberry puree and vanilla extract until fully incorporated.
3. Add a few drops of food coloring if a deeper purple or blue hue is desired.

Decorate the Cupcakes:

1. Pipe a generous swirl of blueberry buttercream onto each cooled cupcake.
2. Top with a fresh blueberry for a beautiful finishing touch.