Preheat oven to 350F.
Blend the sugar and potato starch together until fine and floury in texture.
In a large mixing bowl, add butter and blended sugar/potato starch. Beat with an electric mixer on medium speed until the mixture has paled and is creamy.
Add the vanilla extract and egg, and beat once more until well combined.
Sift in the flour, vital wheat gluten, salt, and baking soda and mix until a soft dough forms.
Add the lemon juice, lemon extract, and lemon zest. Mix to incorporate all ingredients into the dough.
Shape the dough into 20 balls (slightly overfill a tbsp measure) and place onto a parchment lined baking tray. Bake in the preheated oven for approx 12-15 minutes until the edges begin to turn golden. .
Allow the cookies to cool on the tray for 2 minutes before removing and transferring the cookies to a wire rack to cool completely
Enjoy and store any leftovers in an airtight container in the refrigerator for up to two weeks. To freeze, wrap each cookie or keep them divided by using parchment paper and store in a ziplock bag for up to three months.