1. In a large bowl, slightly beat the egg yolks to break them up. Heat heavy cream, milk, and sugar to a simmer in a large heavy saucepan. Slowly pour the hot the milk mixture over the eggs and return combined mixture to the saucepan and slowly cook on medium heat until the mixture coats the back of a spoon. Stir in the lemon juice and zest.
2. Refrigerate for several hours. Chun in your ice cream maker according to the manufacturer's directions. (Freeze for and extra hour or two if you like your ice cream a little firmer!)