Preheat oven to 350°F.
Whisk flour, sugar, and salt together in a medium bowl. Whisk the egg yolks, melted butter, lemon juice, and lemon zest in another, larger bowl.
1 cup granulated sugar, 1/3 cup all-purpose flour, 1/2 teaspoon kosher salt, 4 large eggs, 2 Tablespoons salted butter, 1/3 cup Meyer lemon juice, 1 Tablespoon Meyer lemon zest
Add the flour mixture alternately with the milk to the egg yolk mixture, stirring well between each addition.
1 1/4 cups whole milk
Beat the egg whites in another bowl using an electric mixer until stiff peaks form. Gently fold the egg whites into the batter using a rubber spatula, 1/3 at a time.
Pour the batter into a 3-1/2 quart baking dish or divide evenly between 6-8 individual ramekins.
Set the baking dish or ramekins into a larger pan and carefully fill with hot water to create a bath around the baking dish. The water should cup about 1/3 of the way up the outside of the baking dish or ramekins.
Carefully transfer to the oven and bake for 40-45 minutes for a large cake or 22-28 minutes for individual ramekins, until a light golden brown.
Carefully remove the pan from the oven and take the cake out of the water bath. Let it cool for 10 to 15 minutes before dusting with powdered sugar and serving with fresh berries, if desired.
Berries