Set your oven to 175°C.
400ml plain flour
2 tsp baking powder (or 1 tsp cream of Tartar and 1 tsp bicarb )
Melt the butter and let it cool slightly.
Crush the saffron in a mortar and pestle (a bit of sugar helps to grind it).
Whip the egg and sugar until really fluffy, add the saffron, melted butter and milk.
Mix the baking powder with the flour and fold it into the eggy milky buttery liquid.
Pour into the spring form and bake for approximately 45 minutes.
Sprinkle with icing sugar before serving.