Lemon Curd

(it's from 3 eggs&3 lemons)

Recipe (found here): 1 egg, 1 lemon, 60 g. sugar, 60 g. butter.
On water bath to melt the butter with the sugar, lemon juice and lemon zest. Add frothed egg and whisk on water bath until thick (about 3-4 minutes). Cool it.