Sift the flour into a large bowl and mix it with the xanthan gum.
Add the frozen butter into small cubes. Rub the butter with the flour until the mixture resembles breadcrumbs.
Sift the icing sugar on top and mix.
Add the lemon zest and rub again so all ingredients come together.
Beat the egg in a separate bowl and add it gradually. Use a fork or a spoon to knead/mix it until it forms a ball of dough that may be slightly sticky.
Wrap the dough in cling wrap film and place it in the fridge for 30 minutes . It’s very important this step because it will make easier to work with the dough.
Preheat the oven to 180°C/350°F.
When the dough is cold enough, roll out into a parchment paper about 3mm/ 1/8” thick or on a floured work surface, or between two shets of lightly floured parchment paper.
Use cookie cutter.
Since I don't have a strawberry shape cookie cutter, I did the following. I used a heart and a star design with 6 spokes. For every star I cut, I cut 2 hearts. The star, as you will see in the photos, I cut it in half.
I placed the heart, made holes with a fork and placed the half star on top. This is how the strawberry was formed.
Cut and place your cookies in a baking tray lined with parchment paper. Bake in the oven for about 12 minutes (depending on how powerful your oven is) until golden brown.
Let your cookies cool down well. Spread jam on the halves and then place the remaining halves on top.
Optionally sprinkle them with icing sugar before serving.
