Prepare the utensils and the ingredients. The sugar with the lemon zest finely grated, the other amount of sugar, the lemon juice and the butter, the cornstarch and the eggs.
First pour the lemon zest with the sugar onto the lemon juice and the butter pieces in the saucepan and bring to a boil. Then beat together the eggs with the remaining sugar until the mixture has slightly whitened. Add the cornstarch still stiring. When the butter mixture is up to a boil pour slowly onto the egg mixture and keep stiring delicately.

Pour again into the saucepan. Place it onto medium heat, don’t stop whisking, cook the cream until boiling and remove from the heat. Transfer the cream to the sieve, scraping well the inside of the saucepan. Strain the cream through the sieve with a small ladle. Scrape down the sides of the sieve. When the cream is ready, spoon the cream into the pre-baked tart shells.
Let the garnished tarts cool down then place into the refrigerator.