UPDATE 6/10/13: Also works with Meyer lemon instead of regular lemon and full-fat coconut milk instead of cow's milk.
from The Perfect Scoop by David Lebovitz
3 cups whole milk
3/4 cup sugar
6 Tbsp freshly squeezed lemon juice (from 2 to 3 lemons)
In a medium, nonreactive saucepan, mix 1 cup of the milk with the sugar. Grate the zest of the lemon directly into the saucepan. Heat, stirring frequently, until the sugar is dissolved. Remove from the heat and add the remaining 2 cups milk, then chill thoroughly in the refrigerator.
Stir the lemon juice into the milk mixture. If it curdles a bit, whisk it vigorously to make it smooth again. Freeze in your ice cream maker according to the manufacturer's instructions.