- Preheat the oven to 175 degrees.
- Whip the eggs until they are frothy. Then add the butter.
- In another bowl, mix together the flour, baking powder and Zùsto, and add this to the egg mixture.
- Squeeze the orange and add it to the mixture along with the buttermilk. Mix everything together well.
- Slice the other 2 oranges and place in a well-greased baking tin.
- Pour the batter over this.
- Bake in the oven for 50 minutes.
- Turn it over after baking.