Beat the egg yolks, sugar, salt and rum into foam. Add the sifted flour and baking powder, rusks and hazelnuts (pre-grated).
Add the beaten into snow egg whites to the well mixed dough. Then bake in a greased and floured form for about 40 minutes in a moderately hot oven. Remove once cool and cut it into 2 layers.
Fill and cover it with the cake filling. Optionally, you can top it with thin frosting lines in a grid pattern. Add a few nice hazelnuts (shelled) to serve as decoration.
The cake filling can be made by whipping soft butter, powdered sugar and whipped cream.