- 1 cup sugar
- 2 tablespoons unsalted butter, softened
- 5 tablespoons fresh lemon juice, plus the zest of 1 lemon
- 1/4 cup all-purpose flour
- Pinch salt
- 3 large eggs, separated
- 1 1/2 cups milk
In a large bowl, beat together the sugar and butter with an electric mixer until the butter is fully incorporated. Beat in the lemon juice, lemon zest, flour and salt.
In a small bowl, whisk together the egg yolks. Beat the egg yolks into the sugar mixture, followed by the milk. Clean the mixer beaters.
In a second large bowl, beat the egg whites with the electric mixer on medium-low speed until frothy, about 1 minute. Increase the speed to medium-high and continue to beat until the eggs form stiff peaks, 3 to 5 minutes. Transfer about one-quarter of the egg whites to the sugar mixture and stir gently to incorporate. Gently fold the remaining egg whites into the sugar mixture; it is okay if some of the egg whites remain visible.
Divide the batter between the ramekins. Place the cake pan, with the ramekins inside, on the center rack of the oven. Carefully pour water into the cake pan, around the ramekins, until it reaches about halfway up the sides of the ramekins. Bake until the cake is firm and light golden brown, 35 to 40 minutes.
Carefully transfer the ramekins to a cooling rack and let sit at least until the ramekins are cool enough to handle. Serve warm or at room temperature. (If you would like to flip the cakes out so that the pudding is on top, wait until the cakes are completely cooled. Run a knife around the inside of the ramekin, place a small dessert plate on top of the cake, and flip over to release the cake. If necessary, tap firmly on the bottom of the ramekin to dislodge any stubborn bits.) The cakes are best eaten the day they are baked.