Preheat oven to 350°. Place oven rack on middle level. Grease a 9-inch layer cake pan and dust lightly with flour. Beat the egg yolks with an electric mixer or wire whisk; gradually add the sugar (reserving 2 tablespoons) beating until thick and light. Beat in the cognac and almond extract. Mix in the gourmet nuts and flour. Fold in the butter. Beat the egg whites and salt until soft peaks are formed. Beat in the reserved sugar until stiff but not dry. Fold half the egg whites carefully. Turn into the prepared pan. Bake 30 minutes or until browned and top springs back when pressed with the finger. Cool in the pan 10 minutes, run a spatula around the edge and turn out onto a cake rack. Turn right side up and finish cooling. Sprinkle with powdered sugar.