How to Make It
Heat oven to 350° F. Place six 4-ounce ramekins or a 2-quart baking dish inside a large roasting pan.
In a medium bowl, whisk together the granulated sugar and flour; set aside. In a second medium bowl, whisk together the egg yolks and butter until combined. Whisk in the milk and lemon zest and juice. Add the lemon mixture to the sugar mixture and whisk until smooth.
Using an electric mixer, beat the egg whites and salt on medium-high until stiff peaks form, 2 to 3 minutes. In 3 additions, gently fold the egg whites into the lemon-sugar mixture.
Divide the pudding mixture among the ramekins or pour into the baking dish. Dividing evenly, sprinkle with the turbinado sugar. To the roasting pan, add just enough hot water to reach halfway up the sides of the ramekins or baking dish. Bake until the tops are golden brown, 40 to 45 minutes for cakes in ramekins and 30 to 35 minutes for a cake in a baking dish.