Pour lemon straws with cold water and put on fire, bring to a boil, drain, pour cold water again, bring to a boil again and drain. Repeat 3-4 times to remove the bitterness.
Add 70 ml of water and sugar to the zest, the same weight as the zest. Cook for 30 minutes until the syrup forms. Use a slotted spoon to remove the zest. Squeeze the juice from 2 lemons into the remaining syrup, add more sugar to taste, bring to a boil. Pierce the pie with a toothpick and soak the resulting syrup.