Preheat the oven to 350°F and line two baking sheets with parchment paper or silicone mats; measure ingredients and zest lemons.

In a large bowl, cream 1 cup softened unsalted butter with 3/4 cup granulated sugar and 1/4 cup light brown sugar until pale, about 2–3 minutes with a mixer; add eggs one at a time, mixing until combined, then stir in 2 teaspoons lemon zest and 1 tablespoon lemon juice.

Whisk together 2 1/4 cups all-purpose flour, 1 tablespoon cornstarch, 1/2 teaspoon baking soda, and 3/4 teaspoon kosher salt in a separate bowl.

Add the dry ingredients to the wet in two additions on low speed until just combined; use a spatula to gently fold in 1 1/2 cups fresh blueberries, folding only until streaks of purple are minimal.

Scoop the dough into 1.5-tablespoon mounds onto a tray lined with parchment, spacing 2 inches apart; chill the scooped dough for 15-20 minutes to reduce spreading.

Bake at 350°F for 10–12 minutes until edges are lightly golden but centers still look slightly soft and glossy; let the cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool.

Whisk 1 cup powdered sugar with 1 to 1 1/2 tablespoons lemon juice to a pourable consistency and drizzle over cooled cookies if desired.