Beat the eggs until their volume is doubled, gradually add the sugar while still mixing.
Add sifted flour mixed with cocoa and soda. Mix carefully and with few movements to avoid losing the volume of the eggs.
Then add the butter, continue mixing, and add the raisins with the rum.
Line a tray with waxed paper, pour the cake mix and cook in a preheated oven at 180ºc between 30 and 50 minutes (depends on the mold and its thickness).