How to cook
Beat the eggs with the sugar, separate the whites from the yolks. Beat the egg whites with half of the sugar until you have a fluffy mixture.
Separately beat the yolks with the remaining sugar, add water, baking powder and oil to them, then add the sifted flour and continue to mix with a mixer.
Add the egg whites to the mixture and finally add the raisins and walnuts.
Grease the cake pan, pour the mixture, leave 2-3 tablespoons of the mixture and add 1 tbsp. cocoa, stir and pour it in, so you get a marble cake.
Bake in a preheated oven, just on the bottom oven rack at about 300°F (150 degrees), until the mixture fills up the cake pan completely, then increase to 370°F (190 degrees), in order for it to bake evenly. Sprinkle the finished sponge cake with powdered sugar.