Place the hazelnuts on a jelly roll pan and toast them at 350 degrees for about 5 to 10 minutes, until the skins darken and slip off easily. Be careful that they do not burn. Pour the hazelnuts onto a towel, fold the towel over them, and rub to loosen the skins. Go over the hazelnuts one by one to remove the skins. Cool the hazelnuts and grind them, pulsing on and off, in a food processor fitted with the metal blade, making sure they do not become pasty. Set aside.
In a mixing bowl, whisk the eggs and salt until liquid. Whisk in the sugar and continue whisking a minute or two until light. Whisk in the butter. Mix the flour and baking powder and sift over the egg mixture. Fold in gently with a rubber spatula, adding the ground hazelnuts when the flour is almost incorporated and continuing to fold until the batter is smooth. Do not overmix or the cake will be tough.
Spread the batter evenly in the prepared pan. Bake at 350 degrees for about 30 minutes, until firm and well colored. Cool in the pan 5 minutes, then invert onto a rack. Immediately reinvert and cool right side up. After the torta is cool, wrap it well in plastic and store at room temperature.
© 1990 Nick Malgieri. All rights reserved.