Preheat the oven to 350° F. In a large bowl, with an electric mixer on medium speed, cream the butter and sugar until fluffy.
Add the egg yolks, one at a time. Add the lemon zest, lemon juice, and flour, stirring until just barely combined. Stir in the milk and cream until smooth.
In a separate large bowl, beat the egg whites, until they hold soft-to-medium peaks, adding the salt halfway through. Fold into the custard mixture.
Pour the custard mixture into a 10-inch round cake pan and set into a larger pan filled with 1-inch water. Bake for about 50 minutes, or until the custard is just set. Let cool to room temperature.
Serve on a plate or in a glass bowls, garnished with mint leaves or berries.Makes 8 Source: