Blueberry jam and a sweet, lemony glaze top these Lemon Blueberry Thumbprint Cookies.
Preheat oven to 350°F.
In a medium bowl, cream together butter and granulated sugar until smooth.
Mix in lemon zest, egg yolk, and flour until dough comes together.
Chill dough for 15-30 minutes.
Roll dough into 1 1/2 inch balls and place on a cookie sheet lined with parchment paper.
Using a spoon, make a small impression in the center of each ball. Fill each impression with the blueberry jam.
Bake for 10-12 minutes.
While the cookies are baking, mix together confectioners' sugar, lemon juice, and milk in a medium bowl until smooth. Drizzle over warm cookies.