Put heavy cream, milk, sugar, zest and salt in a pot until sugar is dissolved and bring it to boil.

Beat the yolks in a bowl until smooth.

Pour the hot cream mixture into beaten yolks gradually and stirring constantly. Never pour all of them at one time.

Pour this mixture back into the pot and cook over medium low heat until it coats the back of the spoon, for 3-5 minutes. Stir it constantly and don’t let it boil.

Stir in lime juice and cool it until it reaches at room temperature stirring occasionally. Chill in the fridge about 3 hours. The longer the better.

Pour it into your ice cream maker and freeze according to manufacturer’s instructions.

Keep it in an airtight container and freeze until firm, at least 4 hours.