Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Add the egg and vanilla extract to the butter mixture, mixing until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Gently fold in the blueberries.
For the streusel topping, combine the flour, brown sugar, and cinnamon in a small bowl. Pour in the melted butter and mix until crumbly.
Using a cookie scoop or tablespoon, drop dough onto the prepared baking sheet, spacing them about 2 inches apart. Sprinkle the streusel topping generously over each cookie.
Bake for 12-15 minutes, or until the edges are lightly golden. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.