2 large lemons
3 cups heavy cream
About 10 tablespoons turbinado sugar such as Sugar in the Raw
6 large egg yolks
1/2 teaspoon vanilla
Put oven rack in middle position and preheat oven to 325? F.
Finely grate 2 tablespoons zest from lemons into cream in a 2- to 3-quart heavy saucepan. Stir in 7 tablespoons turbinado sugar and a pinch of salt. Heat mixture over moderately low heat, stirring occasionally, until almost boiling, then remove from heat.
Lightly beat yolks in a bowl, then gradually whisk in hot cream. Pour custard through a fine-mesh sieve into a quart-size glass measure and stir in vanilla and 1 teaspoon fresh lemon juice. Divide among ramekins.
Arrange ramekins in a roasting pan and bake in a water bath until custards are just set around edge but centers wobble when pan is gently shaken, 30 to 35 minutes. Cool custards in water bath 20 minutes, then remove from pan and chill, uncovered, at least 4 hours. (Custards will set completely as they chill.) Sprinkle about 1 teaspoon turbinado sugar evenly over each custard, then move blowtorch flame evenly back and forth close to sugar until sugar is caramelized. Let stand until caramel is hardened, 3 to 5 minutes.
Custards can be chilled, covered with a sheet of plastic wrap after 4 hours, up to 2 days. Very gently blot with paper towels before sprinkling with sugar and caramelizing.