Preheat the oven at 160 degrees Celsius.
Butter an oven form 20 cm in diameter, or an oven form 20x 20 cm.
Separate the egg yellows from the egg whites. Place them in 2 different bowls.
Whip the egg whites to a hard foam.
Mix the egg yellows and the sugar until it becomes pale yellow almost white in the color. It takes approximately 1-2 minutes.
Melt the margarine together with the saffron in a casserole while stirring. Take it away from the heat.
Add the melted margarine and the vanilla extract with the egg yellows. Whip for 1 minute.
Heat the milk to lukewarm and add in the egg yellow batter. Mix well.
Slowly fold the egg white foam in the batter. It will be small lumps on the surface.
Pour the batter in the oven form.
Place in the middle of the oven for 50 minutes.
Check that the cake isn’t jiggly before taking it out from the oven. If so, cook a little bit longer.
Take out the cake and let it cool down in room temperature.
Place the cake on a serving plate and let it in the fridge for minimum 3 hours before serving.