Preheat oven to 180°C (350°F).
Place tart shell in tart pan and prebake if needed.
In a bowl, whisk together condensed milk, lemon juice, lemon zest, egg yolks, and melted butter.
Pour filling into prepared tart shell.
Bake for 15–18 minutes until filling is just set.
Remove from oven and cool completely.
Chill for at least 2 hours before serving.
Dust with powdered sugar before slicing.