Preheat oven to 350 degrees.
Butter eight 3/4 cup ramekins or custard cups. Whisk 1/2 cup plus 2 tbsp sugar, flour, and pinch of salt in medium bowl to blend. Combine milk, egg yolks, lemon juice, and lemon peel in large bowl; whisk until blended. Add flour mixture to yolk mixture and whisk custard until blended.
Using electric mixer, beat egg whites in another large bowl until soft peaks form. Gradually add remaining 1/4 cup sugar to whites and beat until stiff but not dry. Fold 1/4 of whites into custard. Fold remaining whites into custard in 2 additions (custard will be slightly runny).
Divide custard equally among prepared ramekins. Place ramekins in large roasting pan. Pour enough hot water into pan to come halfway up sides of ramekins. Bake custard cups until golden brown and set on top (cakes will be slightly soft in center), about 27 minutes.
Chill custard cakes uncovered until cold, at least 4 hours, then cover and keep refrigerated. Can make one day ahead.
Using electric mixer, beat creme fraiche in medium bowl until softly whipped.
Run small knife aoround each custard cake to loosen. Invert each cake onto plate. Place dollup of creme fraiche atop or alongside cakes and serve.