I do apologize for not knowing anything other than US measurements for baking and cooking.
3 large lemons (or 6 small ones)
1 cup sugar
4 eggs + 1 extra egg yolk
10 tablespoons cold unsalted butter (and yes, it does have to be real butter, margarine doesn’t work)
3 tablespoons heavy cream
Zest one whole lemon. Juice all the lemons and add the juice, the zest, and sugar in a non-reactive pan. Stir until all is combined, and then heat until the sugar is no longer granular (not quite at boiling). Take off heat and let cool. Meanwhile, whisk all the eggs and extra egg yolk together, along with the cream until well beaten. Cut the butter into smallish cubes. Once the lemon mixture is not so hot (but still warm) add a small bit to the egg mixture to temper the eggs. Add the tempered eggs into the pan, along with the butter. Cook over medium-low heat, stirring constantly, until the butter is all melted and the curd thickens up.
Take off heat and put the curd through a strainer to strain out all the solids (stray seeds, the zest, etc). Store in the refrigerator for a week. Or, you can freeze it for up to 3 months.
This produces about a pint of lemon curd. It’s a bit on the tart side, so if you like sweeter, add a bit more sugar.
This can be served with pound cake, as a filling for a layer cake, as a dipping sauce for shortbread cookies, in mini pie shells as tartlets, as filling for thumbprint cookies … If you think of other things to serve it with, let me know! I’ve heard of putting it into plain yogurt, but I’ve never had enough Lemon Curd left over to try it in my morning yogurt! One of these days…
Oh, this recipe can be doubled, but to try and make more than one double recipe at a time will result in burning, no matter how careful you are. At least, it always has for me.