Cream fat, eggs and sugar. Mix baking powder, flour and salt and stir in by the spoonful. Wash the orange. Dab 1 fruit dry. Grate the peel thinly, squeeze out the juice and stir both into the dough.
Peel and slice the remaining oranges. Line the bottom of a springform pan (26 cm Ø) with baking paper. Put orange slices on top. Fill in the dough and smooth it down. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for 55-60 minutes.
Let it cool down. In the meantime, heat up the jam and pass it through a sieve. Turn the cake over onto a cake rack and spread with jam. Serve with crème fraîche seasoned with vanilla sugar.
The cake is 16 pieces.