Make the blueberry cupcakes:

1. Preheat the oven to 350°F. Prepare a 12-tin muffin pan by lining with cupcake liners.
2. In a medium mixing bowl, toss together the blueberries and 1 tablespoon of flour. Set aside.
3. In a separate medium sized bowl, add the flour, baking powder, and salt. Whisk together to combine.
4. In a large mixing bowl, add butter and sugar. Use an electric mixer and beat on medium-high until light and fluffy looking, about 3-4 minutes. Add in the eggs and vanilla, then beat again until well incorporated and smooth.
5. Add 1/3 of the flour mixture to the large bowl, then mix on low until combined. Add ½ of the sour cream and mix on low until combined. Continue alternating the flour mix and the sour cream, until both have been completely added (finishing with the flour mixture). Fold in the flour-covered blueberries.
6. Divide the batter into the cupcake tin. Place the tin into the oven and bake for 20 to22 minutes, or until an inserted toothpick comes out clean. Allow to cool for 5 minutes, then transfer to cooling rack. Allow to cool completely before frosting.

Make the blueberry frosting:

1. Place the blueberries and lemon juice into a saucepan or skillet and heat over medium heat. Bring to a simmer, while stirring frequently and mashing the blueberries as they soften. Continue to simmer until the compote has thickened slightly and tastes slightly less tart (it will still taste slightly tart though), about 10 minutes. Remove from the heat and allow the compote to cool to room temperature.
2. Add the butter to a stand mixer fitted with the whip attachment. Beat on high until fluffy and pale, about 3-4 minutes. Turn to low, then begin adding the confectioners’ sugar. Once all of the sugar has been added, add the blueberry compote, vanilla and salt, then beat on high until very smooth and fluffy, about 2 minutes. Use a spatula to scrape at the bowl occasionally to ensure even mixing.

Frost the cupcakes:

1. Add the frosting to a piping bag fitted with a large closed-star tip.
2. Pipe the frosting onto each cupcake. Finish with 3 blueberries on each cupcake, if desired.