1.
Preheat the oven to 180°C (fan).
2.
Melt the butter in a pan over low heat. Put eggs and sugar in a mixing bowl and whisk until foamy, then add the melted butter.
3.
In a separate bowl, mix flour, baking powder, orange zest, and two pinches of salt well. Then combine everything thoroughly.
4.
Bake in a greased pan for about 30 minutes and let cool.