Sift the flour, baking powder in a bowl, stir.
Break the eggs in another bowl, add the sugar and grated rind of the lemon, stir very well to a fluffy cream. Pour the oil in a thin trickle and beat with the mixer until you get a mayonnaise-like mixture.
Pour in the lemonade and stir, add the flour in stages - this time stir with a spatula to a homogeneous fluffy mixture.
Smear a round cake form with butter and stick the raisins along its bottom and sides.
Pour in the mixture and place the form in a cold oven. Turn it up to 356°F (180 °C) and bake about 35 min. until ready, while checking its inside with a toothpick.
Besides being really fluffy it's also extremely tasty!