Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy, about 3 to 4 minutes using an electric mixer on medium speed.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract, lemon zest, and lemon juice until combined.
In a separate medium bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, and cornstarch.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Gently fold in the fresh blueberries, taking care not to crush them.
Using a cookie scoop or spoon, drop large mounds of dough (about 2 tablespoons each) onto the prepared baking sheets, spacing them about 2 inches apart.
Using your fingers or the back of a spoon, gently flatten each mound slightly to form muffin-top shapes.
Bake in the preheated oven for 10 to 12 minutes, or until the edges are golden and the centers are set but still soft.
Remove from the oven and allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.