Prepare the Cookie Dough:
Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, cream together the butter and sugar until light and fluffy.
Add the egg, vanilla extract, lemon zest, and lemon juice, mixing until fully combined.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.
Gently fold in the fresh blueberries, being careful not to crush them.
Bake the Cookies:
Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Flatten each cookie slightly with the back of a spoon or your fingers.
Bake for 12-15 minutes, or until the edges are lightly golden and the centers are set.
