Put the almond flour and sugar in a bowl and add the egg and lemon zest. Keep stirring and mixing until you have a kneadable mixture. Add a little extra egg if it remains too dry.
Knead the almond paste into a cube or roll and wrap in cling film. For best results, place your almond paste in the refrigerator at least overnight.
However, the almond paste can also be processed immediately. In that case, make the paste before you start the recipe and put it to rest in the refrigerator until you need it.
Tips
Make a larger amount of almond paste and freeze it in portions.
How to store
Unbaked almond paste can be stored tightly covered in the refrigerator for up to a week, or in the freezer for up to 3 months.