Lemon Sponge Custard

Yield:	6 Servings
Categories:	Puddings, Custards, Desserts

2	tb	Unsalted butter; softened
2/3	c	Sugar
1/8	ts	Salt
3	lg	Egg yolks
3	tb	All-purpose flour
1/4	c	Strained fresh lemon juice
2	ts	Grated lemon zest; (up to 3)
1	c	Whole milk
4	lg	Egg whites at room temperature