Beat the eggwhites until stiff.Add the sugar little by little.Fold in the chopped nuts and the vanilla. Bake in well greased and floured pan until golden brown.
Make syrup with the sugar and the water until it spins a thread. Pour in the syrup to the beaten eggyolk little by little. Add the butter and beat it until thick. Add flour with baking power, beat until thick. Add rum and decorate cake.