Whisk together eggs and yolks in a medium-sized saucepan. Individually whisk in sugar, lemon juice and zest. Add in butter and cook over medium heat until mixture begins to thicken -- around 140F on a candy thermometer. **MAKE SURE FILLING DOES NOT BOIL**
Remove immediately from heat and strain through a stainless sieve into a bowl. Cover surface with plastic wrap and cut 5-7 small slits in wrap to allow steam to escape. Refrigerate curd to thicken. Filling will keep up to two weeks.
To assemble: arrange tartlet shells on baking sheet and fill with 1 tsp of chilled filling. Cook for 5 minutes at 350F or until filling sets. Remove to cooling rack. Once cooled brush apricot jam over filling.