Step 1: Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper or silicone mats.
Step 2: In a medium bowl, whisk together 1 ¾ cups all-purpose flour, baking soda, and salt. Set aside.
Step 3: In a large bowl, using an electric mixer, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 2-3 minutes.
Step 4: Beat in the egg and vanilla extract until well combined. Scrape down the sides of the bowl as needed.
Step 5: Add the lemon zest and lemon juice to the wet ingredients and mix until just combined.
Step 6: Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
Step 7: In a small bowl, gently toss the fresh or frozen blueberries with 1 tablespoon of flour.
Step 8: Fold the floured blueberries into the cookie dough by hand using a spatula until evenly distributed.
Step 9: Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.
Step 10: Bake for 10-12 minutes, or until the edges are lightly golden and the centers are still soft. Do not overbake.
Step 11: Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.