Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.
In a large bowl, cream together the softened butter and 1 cup of powdered sugar until light and fluffy.
Beat in the egg, vanilla extract, lemon zest, lemon juice, and lemon extract, if using. Mix until just combined.
In a separate bowl, whisk together the gluten-free flour blend, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until a soft dough forms. Do not overmix.
Roll the dough into 1-inch balls. Roll each ball in additional powdered sugar until fully coated. Place balls 2 inches apart on the prepared baking sheets.
Bake for 10 to 12 minutes, or until the edges are set but the centers still look slightly soft. They will firm up as they cool.
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.
Prepare the glaze: Whisk together the 1/2 cup powdered sugar and 2 tablespoons of lemon juice until smooth.
Drizzle the glaze over the cooled cookies. Let the glaze set before serving.
Notes
Use a high-quality gluten-free flour blend that contains xanthan gum for the best texture.
For a stronger lemon flavor, increase the zest to 1 1/2 teaspoons.
These cookies achieve their meltaway texture because they are slightly underbaked; they firm up during cooling.
Store cookies in an airtight container at room temperature for up to 4 days.