In a large bowl, using an electric mixer, beat the egg whites with the cream of tartar and salt at low speed until frothy. Add 2 tablespoons of the super- fine sugar and increase the speed to medium. Add another 2 tablespoons of superfine sugar and beat for 30 seconds. Increase the speed to high and slowly beat in the remaining 1/4 cup of superfine sugar. Beat for about 5 minutes, until the meringue is stiff and glossy. Fold in the hazelnuts.