Break the eggs in a bowl, add the sugar, put the bowl in a water bath and beat with a mixer for 15 min. until you get a very fluffy and soft mixture. While stirring nonstop, add the oil, vanilla and lemon rind which you've grated on a fine grater. Stir until homogeneous.
Put the mixer down and start stirring slowly with a spatula from the bottom going up, add the sifted flour in several lots until fully absorbed.
Smear the cake form with soft butter. Grab a handful of raisins, use them to scoop up soft butter, 1 by 1, and arrange them along the bottom and sides of the form.
Pour 1/3 of the mixture into the form, then sprinkle 1 tsp cocoa through a sieve on top. Place another 1/3 of the mixture on top, cocoa again and finish with the final 1/3 mixture.
Place the form in a preheated 302°F (150 °C) and bake until ready, check to see if it's ready with a toothpick.
An amazingly fluffy and aromatic cake without raising agents!