This is a very simple, yet delicious, dessert made with a few basic ingredients: ground walnuts, eggs, sugar and lemon. With its soft consistency and its nutty flavour, this cake is the perfect companion to a hot cup of tea on cold winter's afternoons. You can serve it 'au naturel', sprinkle it with some icing sugar or use it as a base and garnish it with a chocolate or mascarpone ganache.