Beat the eggs with the sugar until fluffy and white. Then add the vanilla seeds and the orange or bergamot zest. Beat for another minute, stop and then add the walnuts, stirring softly. Gradually add the breadcrumbs, baking powder and continue stirring. For the syrup: Boil the water, sugar, lemon juice and vanilla stick for 4 minutes. Add the skin of the orange and lemon and let boil for two more minutes.