Preheat oven to 350 degrees and grease an 8x8x2 shallow baking pan.
Scald milk in a small pan to 180 degrees, stirring constantly so the milk doesn't burn or form a crust. Set aside and let it cool to 110 degrees.
While milk is cooling, combine sugar, flour, salt and butter. Add lemon juice and grated lemon rind. Set aside.
Separate eggs into yolks and whites into two different bowls. Beat egg yolks and the cooled milk together. Add mixture from step above to the egg yolk and milk mixture. Mix well.
Beat egg whites until there are stiff peaks. Fold egg whites into mixture and then pour into the 8x8x2 greased, shallow baking dish. Bake at 325 degrees for 45 minutes. When baked, custard is on the bottom and cake on top.
