Coarsely chop the walnuts, roast them in a pan without fat until golden brown, take them out and let them cool down. Wash oregano, shake dry and chop. Grate cheese finely
Mix flour and baking powder. Beat the eggs and oil with the whisk of the hand mixer until foamy. Gradually add flour mixture, buttermilk, cheese, oregano and walnuts. Season with salt and pepper
Grease a box form (26 cm long) and dust with flour. Pour in the dough and bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 55 minutes. Take out the cake, let it rest for about 10 minutes and carefully turn out of the tin. Serve hot or cold