Preheat the oven to 350°F (180°C) and prepare a baking sheet with parchment paper.
In a large bowl, combine the softened butter, brown sugar, and lemon zest. Use a mixer to beat well until the mixture is creamy and smooth.
½ cup butter, 2 teaspoon lemon zest, ¼ cup brown sugar
Add the lemon juice and egg, and beat well until fully integrated.
1 tablespoon lemon juice, 1 egg
In the same bowl, add the flour, baking powder, baking soda, and salt. Mix until the dry ingredients are well incorporated.
½ teaspoon baking powder, ½ teaspoon baking soda, ⅓ cup flour, ⅛ teaspoon salt
Gently fold in the fresh blueberries with a spatula, mixing carefully to avoid breaking the blueberries.
½ cup fresh blueberries
Use a #20 cookie scoop to form the cookies and place them on the prepared baking sheet, leaving space between each one.
Shape each cookie into a round form and make a small indentation in the center with your finger or the back of a spoon.