Place the butter in a bowl and add the lemon zest. Microwave on full power for 30 seconds or until melted. Allow to cool.
Beat together the egg yolks, crème fraiche, sugar, cooled melted butter and milk. Gently fold in the flour, the beat very briefly to remove the majority of lumps. Don't worry if there are a few lumps.
Whip the egg whites until stiff, and then using a metal spoon, gently fold into the flour mixture in two stages.
Grease a pan with butter and allow to foam a little bit. Use an ice cream scoop to drop spoonfuls of the batter onto the pan, allowing room for spreading around each pancake.
Cook on a medium-low heat until the top begins to bubble all over. Flip and cook on the other side for a minute or until golden.
These pancakes are good naked but if you have a sweet tooth, drizzle with a little bit of golden syrup.