Preheat oven to 350 degrees F. Line a muffin tin with paper liners and set aside.
In a large bowl, sift together the flour, sugar, baking powder, salt and baking soda.
In a medium bowl, whisk together the softened butter and egg until combined, then add the buttermilk, beer, lemon zest mixture and lemon juice. Whisk well until all ingredients are combined.
Add the beer mixture to the flour mixture and stir together until just moistened. Do not over mix.
Gently fold in blueberries. Spoon batter into each liner, filling about 2/3 the way full. Bake for 25 minutes, or until golden brown. Remove from oven and let chill completely.
For the frosting
Add beer and blueberries to a saucepan over medium heat. Simmer for about 10 minutes until beer is thickened and reduced to about 1/4 cup, stirring continuously. With a mesh sieve over a bowl, strain out the blueberry beer and press all juices from the blueberries into the bowl with the backside of a spatula. Discard the skins and allow the blueberry beer concentrate to cool.
In the bowl of an electric mixer with the paddle attachment, or using a handheld mixer in a large bowl, whisk the butter on high for about 5 minutes or until white and fluffy. Scraping down sides.
Add 3 cups powdered sugar, a cup at a time, mixing on high between additions. Add cooled blueberry beer concentrate and mix well. Whip for 2-3 minutes, adding more powdered sugar if it looks too thin. Use pastry bag or spread onto cooled cupcakes.