Beat the eggs and sugar with a mixer into foam. To the resulting mixture, add the vanilla, then the flour spoon by spoon, stirring slowly so the mixture does not deflate. It is recommended to stir with a whisk.
Pour a little of the mixture into a bowl and add cocoa, mixing well. In a well-greased cake form, pour in some of the yellow mixture, then the cocoa mixture and finally, the remaining yellow mixture. Bake in a preheated oven at 302°F (150 °C) for about 35-40 minutes; do not open the oven during the first few minutes so it does not deflate.
Once the cake has reddened, cover it with foil to prevent burning. Check with a toothpick to see if it is ready.