Marble cake

beat 4 egg yolks with 200 g of sugar, add 150 g of melted but not hot margarine and beat until fluffy. then mix the 200 g of sifted flour and, finally, mix very carefully the 4 egg whites raised in a very firm castle. then divide this appliance into 2 equal parts: in one mix the lemon zest; in the other mix 100 g of powdered chocolate, linking it very carefully. grease the mold very well with margarine and pour the two preparations, chocolate and lemon in alternating layers, then bake in a medium oven for about 25 m. after cooking, let it cool a little and unmold. for the topping: in a pan, mix the remaining 50 g of melted margarine with the remaining 100 g of powdered sweet chocolate; bring to the boil until you start to want to bubble and mix well and cover the cake with this icing. let cool and serve.