01 -
Preheat the oven to 375°F (190°C) for about 20-30 minutes before baking. Line a large baking sheet with parchment paper.
02 -
Melt the butter in a small bowl and cool in the refrigerator for about 10 minutes.
03 -
In a separate bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt until well combined.
04 -
In a large mixing bowl, whisk the sugar and lemon zest together until they reach the consistency of wet sand. Whisk in the cooled melted butter until well combined. Add the egg, egg yolk, and vanilla extract, whisking until smooth and well incorporated.
05 -
Stir the dry ingredients into the wet ingredients until just combined. Gently fold in the blueberries until evenly distributed throughout the dough.
06 -
Using a medium cookie scoop (2 tablespoons, 30 ml), portion the dough into balls. If desired, roll each ball in granulated sugar. Place on the lined baking sheet, spacing them about 3 inches (8 cm) apart.
07 -
Bake at 375°F (190°C) for 10-12 minutes or until the edges of the cookies are set and light golden brown.
08 -
Allow cookies to cool on the baking sheet for 3-4 minutes before transferring to a cooling rack to cool completely.