Melt butter in a pot. Separate the eggs. Beat egg yolks, 1/2 teaspoon salt and sugar for about 4 minutes until light creamy. Mix flour and baking powder. Alternately stir in flour-mix and butter. Beat egg white until stiff.
Stir 2 tablespoons into the egg mixture, fold in the remaining beaten egg white. Spread the dough onto 3/4 of the baking tray lined with baking paper and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see
manufacturer) Bake for 8-10 minutes. Turn the sponge cake onto a damp tea towel, roll it up with the towel and let it cool down.
Cut salmon into wide strips. Wash the dill, shake dry and cut the flags into small pieces, except for a few for garnishing. Mix ricotta and chopped dill, season with salt and pepper.
Unroll the sponge cake. Stir taramas until smooth and spread on top. Spread salmon strips on the taramas and cover with the ricotta. Roll up the sponge cake from the long side, wrap in cling film and chill for about 1 hour.
Just before serving, cut the roll open and garnish with dill and caviar.