Preheat the oven to 150°C fan and line 2 baking trays with baking paper.
In a mixer, cream together the butter and sugar until well combined,
125 g unsalted butter, 100 g white caster sugar
Add the egg, egg yolk, lemon zest and vanilla and whisk again until thoroughly incorporated. Do not overmix as an over aerated mixture will give too much rise to the biscuits.
1 medium egg, 1 medium egg yolk, zest from 1 lemon, ½ tsp vanilla extract
In a separate bowl. combine the flour, ground almonds, salt and Xanthan Gum and whisk until combined. Add the to wet ingredients and mix on a medium speed until a sticky dough forms.
250 g gluten-free plain flour blend, 100 g ground almonds, ½ tsp Xanthan Gum, ¼ tsp salt
Wrap the dough in clingfilm and place in the fridge to film up for a minimum of 30 minutes to 1 hour.
Remove the dough from the fridge and leave on the kitchen counter for 5 minutes before cutting the ball of dough in half and rolling out each half between two sheets of baking paper to a thickness of approximately 4-5mm. Try to avoid using any extra flour as this will dry out the dough too quickly.
Place the rolled out dough back in the fridge for a further 15-30 minutes to chill. This will help when cutting out the biscuits in the next step.
Remove from the fridge and cut out the biscuits using a 1 ½ inch round fluted cookie cutter. You will need 1 top biscuit and 1 bottom biscuit for each linzer sandwich. Use a smaller circular cutter to cut out a hole in the centre of each top biscuit.
Place the biscuits on a lined baking tray, leaving 2cm gaps between each one.
Bake on the middle shelf for around 8 minutes. The edges of the biscuits will be starting to turn a golden brown colour, but the biscuits should still generally be pale in colour.
Allow the biscuits to cool on the baking tray, before transferring them to a cooling rack to cool completely to room temperature.
Once cooled, dust a layer of icing sugar over the top biscuits using a small sieve, and then spoon a small teaspoon of lemon curd onto the bottom layer biscuits before sandwiching them together.
4-5 tbsp lemon curd, icing sugar