It's a really light sponge cake filled with lemon flavoured cream, you can make it easily and fast. First separate the egg yolk and white into two bowls. Than preheat the oven to 180 C degree and prepare a buttered-floured cake pan. Mix the sugar with egg yolk until foamy and light yellow. Than whisk the egg white to very hard foam and pour into egg yolk mixture. Add 2 tablespoon flour and stir it gently with kitchen spoon. Stir always into one direction. Than add another two spoon of flour and stir it 3 times and add the last 2 tablespoon of flour. Take care of stirring, don't smash the egg white. Mold into cake pan and place into oven immediately. Bake it approx 10 minutes on 180 C degree than reduce the heat to medium and bake it 20 minutes. Thrust a toothpick into the middle of the cake whether is it baked or not. If the toothpick remained dry than the cake is baked. Take out of the oven and let it cool down at least 10 minutes before remove from the pan.
Set a heatproof bowl over a pan of simmering water, being careful that the bottom of the bowl does not touch the water. Place the lemon zest and juice, sugar and butter into the heatproof bowl. Stir with a whisk from time to time until the butter has melted. Stir the eggs and egg yolk into the lemon mixture. Let the curd cook, stirring regularly, for about 10 minutes, until it is thick and custard-like. It should feel heavy on the whisk. Remove from the heat and stir occasionally as it cools. Cut into half the sponge cake and fill with lemon curd. Sprincle the top of the cake with icing sugar and serve with pear or apple compote.