Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.
Cream together butter and sugar for 3–4 minutes until light and fluffy.
Beat in egg, lemon zest, and lemon juice until fully combined.
In a separate bowl, whisk together flour, baking soda, and salt.
Gradually mix dry ingredients into the wet mixture until just combined.
Toss blueberries with 1 tbsp flour, then gently fold them into the dough with a spatula.
Scoop 1.5-tablespoon portions of dough onto prepared baking sheets.
Bake for 10–13 minutes, until edges are lightly golden and centers are just set.
Let cookies cool on baking sheet for 5 minutes before transferring to a wire rack.
Optional: Once cooled, drizzle with lemon glaze.