Combine blueberries with 2 tablespoons of lemon juice and 1 tablespoon of lemon zest in a medium bowl. Let sit for 15 minutes.

In a large bowl, cream together butter and sugar with an electric mixer for 3-5 minutes until light and fluffy.

Gradually mix in powdered sugar, egg yolk, vanilla extract, lemon juice, and lemon zest until smooth.

In another bowl, whisk together flour and salt, then gradually add to the wet mixture until combined.

Gently fold the blueberry mixture into the dough without crushing the blueberries.

Cover dough with plastic wrap and chill for at least 2 hours or overnight.

Preheat oven to 350°F (175°C). Line baking sheets with parchment paper. Drop spoonfuls of dough spaced apart.

Bake for 12-15 minutes until edges are golden brown and centers are soft.

Allow cookies to cool for 5-10 minutes, then transfer to a wire rack.

Whisk reserved egg white with powdered sugar and lemon juice to create a glaze, and drizzle over cooled cookies.