Step #2 At lowish speed cream butter, margarine, & sugar during 30 mins (sound like a lot but trust me -- it's the key to the texture, meanwhile prepare the rest of the ingredients).
Step #3 Add the yolks to the mixture one by one, until they are incorporated in the mixture.
Step #4 In a separate bowl mix orange juice, vanilla & rum.
Step #5 Sift flour & baking soda, together.
Step #6 Alternating add to the mixture the flour & the juice.
Step #7 Add about a spoonful of flour to the raisins & cut them a bit, this will avoid to have raisins only at the bottom of the cake ;-).
Step #8 Set aside, & beat the egg whites until they are fluffy but not totally firm.
Step #9 With a wooden spoon mix the whites into the mixture.
Step #10 Pour into the mold (previously greased & floured) & spread it around leaving a small depression in the center, this way when it grows during baking it won't curve up.
Step #11 Bake for 35 mins or until it is golden & the cake has separated from the mold.