24 hours before making ice cream with an electric ice-cream maker, place the freezer bowl in the freezer. Check your ice cream maker manual for specific instructions.
In a small sauce pan, heat the cream, milk, lemon extract, vanilla extract and lemon zest on medium-low for 15 minutes. Be sure to stir occasionally and not to let it boil.
Meanwhile, in a large mixing bowl, add the yolks and sugar. With a whisk, break the yolks and combine with the sugar.
Remove the liquid from the stovetop and quickly strain the liquid into a large measuring cup. Working quickly, temper the yolk mixture. To temper the yolks, whisk the eggs quickly while slowly adding the warm liquid (about 1/4 cup at a time) until all the liquid is combined.
Once the yolks have been tempered, add the freshly squeezed lemon juice and stir well to combine.
Cover the bowl and place in the fridge. Let it chill for at least 2 hours, up to 24 hours.
Place the ice cream mixture into the ice cream maker and mix for 20 minutes, or until the ice cream is thickened to the desired consistency.
Serve immediately for soft serve, or place in a freezer safe container and freeze for a firmer texture.