In a large mixing bowl, use an electric mixer to cream together the butter and powdered sugar for about two minutes. Mix in the egg and lemon juice. Set aside.
In a medium-sized bowl, sift together the flour, lemon zest, baking soda, and cream of tartar. Gradually add the dry ingredients to the bowl of wet ingredients as you mix the dough. Scrape the sides of the bowl with a rubber spatula to fully incorporate the ingredients. Finally, gently fold the blueberries into the dough with a rubber spatula or wooden spoon.
Cover the bowl with plastic wrap and chill in the fridge for 1-2 hours.
When you're ready to bake the cookies, preheat the oven to 350℉. Line two baking sheets with parchment paper and remove the dough from the fridge. Use your hands or a cookie scoop to roll out 2-tablespoon-sized cookie dough balls and place them on the baking sheet making sure to separate the cookies 2 inches apart. Bake for 9-11 minutes or until the cookies are just starting to get golden brown.
Allow the cookies to cool on the baking sheet for about 10 minutes before transferring to a wire rack to cool completely.