Preheat your oven to 375°F (See Recipe Notes). Line a rimmed baking sheet with unbleached parchment paper and set it aside.

In a large bowl, place the flour, xanthan gum, cornstarch, baking powder, salt, granulated sugar, and lemon zest. Whisk to combine well, breaking up any clumps of zest.

Create a well in the center of the dry ingredients and add the butter, eggs, and lemon juice. Mix until all the ingredients are just combined. Be careful not to overmix.

Scoop the dough into portions about 1.5 tablespoons each with a spring-loaded ice cream scoop or two spoons. Place about 2-inches apart on the prepared baking sheet. Using clean fingers, pat down any very rough dough around the edges (but not on top).

Lift each mound of cookie dough gently and place into the confectioners’ sugar (See Recipe Notes) and toss to coat. Allow the dough to sit briefly, and then toss it in confectioners’ sugar again.

Return the mounds to their positions on the baking sheet.

For insurance, moisten the tops of the fully prepared mounds of dough, dust lightly with more confectioners’ sugar, and then brush off the excess with a pastry brush.

Place the baking sheet in the center of the preheated oven. Reduce the oven temperature to 350°F right away (See Recipe Notes).

Bake until the cookies are puffed and mostly set in the center (about 12 minutes; don’t over bake). Remove from the oven and allow to cool completely on the baking sheet before serving.