1. In a small pot over a low flame, heat the milk, 1/2 cup of cream, the sugar, and half the zest until sugar dissolves, about 5 minutes. Do not boil. Let cool.

2. Beat the egg yolks in a bowl with the cooled milk mixture until combined. Pour into a pot and cook over low heat, stirring constantly with a wooden spoon, until the mixture thickens to a custardlike consistency. Be careful not to let the mixture get too hot or the eggs will cook. Strain, and add remaining tangerine zest.

3. Add the tangerine juice and up to 2 teaspoons lemon juice to the mixture. Whisk together and chill. Pour into an ice-cream maker and freeze according to manufacturer's instructions.