In a large mixing bowl, using an electric mixer on medium speed or a wooden spoon, beat together the butter and both sugars until light and creamy. This will take about 3 minutes if using an electric mixer or 5 to 6 minutes if creaming by hand. Add the lemon zest and lemon juice and beat to combine. Add the flour and salt, and beat on low speed or by hand until the dough comes together about 1 minute. Using a rubber spatula, fold in the blueberries until incorporated.
Place the dough between two sheets of wax paper or parchment paper. Using a rolling pin, roll out the dough to an even ½-inch thickness. Wrap the dough in the paper and refrigerate until firm, about 30 minutes.
Preheat the oven to 350ºF. Line a cookie sheet with parchment paper.
Using a 2-inch round cookie cutter, cut out the cookies and place them 2 inches apart on the prepared cookie sheet. Rechill if they seem soft.
Bake 14-15 minutes until edges are golden brown. Start checking at 12 minutes!
Let the cookies rest on the sheet for 5 minutes before transferring to a wire rack to finish cooling.
Like many shortbread, flavors will develop and the cookie will be even better the next day!