In the bowl of a stand mixer fitted with the paddle attachment, combine both sugars and the lemon zest. Using your fingers, rub the lemon zest into the sugars for about 20 seconds to help intensify the lemon aroma and flavor in the final cookies.

Add the softened butter to the sugar mixture and beat on medium-high speed for about 3 minutes, or until the mixture becomes light and fluffy. Pause the mixer and scrape down the sides of the bowl with a spatula to ensure everything is well incorporated.

Add the room temperature egg and vanilla extract, then mix on low speed until fully combined. Scrape the bowl once more to ensure even mixing.

In a separate mixing bowl, whisk together the flour, baking soda, cream of tartar, and kosher salt. Gradually add the dry ingredients to the butter mixture, mixing on low speed just until the dough comes together. Avoid overmixing—the dough should still have a few visible streaks of flour.

Detach the mixing bowl and use a large spatula to gently fold in the chopped freeze-dried blueberries, being careful not to overwork the dough.

Let the dough chill uncovered in the bowl for 30 minutes. After chilling, preheat your oven to 350°F (175°C). Pour the coarse sanding sugar into a small bowl. Line two baking sheets with parchment paper. Using a medium cookie scoop, portion out the dough and roll each dough ball in the sanding sugar, making sure to coat all sides thoroughly.

Arrange the coated cookie dough balls on the prepared baking sheets, spacing them 2 to 3 inches apart. Bake on the center rack for 8 to 9 minutes, or until the edges are set and slightly golden while the centers remain slightly puffed.

Remove the trays from the oven and let the cookies cool directly on the baking sheets for 5 to 10 minutes. Then, transfer them to a wire rack to cool completely. If desired, sprinkle additional sanding sugar over the tops for added crunch and sparkle.