Mix the eggs, sugar and lemon juice together. Cook over medium heat for about 15 minutes or until your whisk holds most of the crème, revealing the bottom of the pan.
Spoon into a clean bowl and stir in the butter and zest. I use a lot of zest because I like a very tart crème. Adjust for your taste. Chill a few hours.
When cold, stir in the crème fraîche and pour into a pre-baked tart shell. Today I made a pine nut crust. Refrigerate and let rest until set.
To serve, spoon some lemon marmalade over the top. Light and delicious!