Preheat the oven to 350 degrees. Fill a large skillet with enough water to go up the sides by 1/2" and place in the oven. Grease a 9" cake pan or pie plate and set aside.

Whisk together the egg yolks, sugar, flour and salt until combined, then whisk in the butter, milk, lemon zest and juice until incorporated.

Beat the egg whites on medium high speed until glossy and soft peaks form, about 1 minute.

Gently fold 1/3 of the egg whites into the lemon mixture until just combined. Fold in another 1/3, followed by the last 1/3. It's ok to see large fluffs of egg white.

Remove the pan of water from the oven with an oven mitt. Place the prepared pan inside the water bath, then gently pour the batter into the prepared pan and spread evenly as gently as possible.

Bake for 30-35 minutes or until set. Check for doneness after 30 minutes — the cake will wobble ever so slightly when it's done. Gently remove the pan from the water bath and place on a wire rack to cool slightly. Serve warm or allow to come to room temperature. Enjoy!