Preheat oven to 375 degrees F. Combine sugar and butter and beat until fluffy. Add the sifted flour and salt, and then the nuts. Combine into a smooth dough. Place in the refrigerator for 1 hour. Line a shallow cake tray with buttered foil. Remove pastry from the refrigerator and cut in half. Press out to form 2 circles 9 inches in diameter onto well greased foil. Trim to a perfect circle, scraping away excess pastry with a teaspoon. Mark 7 portions on one of the circles. Place into the oven for 8 minutes. Remove and allow to cool. When cool, place the uncut layer onto a serving dish. Mix the raspberries with the sour cream and spread raspberry mixture onto pastry. Place the 7 portions of pastry on top. Leaving a space in between each portion. Whip the cream until stiff. Pipe a whipped cream rosette onto each portion and one in the center and place a toasted hazelnut on each. Sift confectioners' sugar over the cake.