Butter and flour 13x9x2-inch metal baking pan. Bring 1 cup sugar, 1 cup water and 1/2 tablespoon orange peel to boil in heavy small saucepan, stirring often; boil 2 minutes. Refrigerate syrup uncovered.
Finely grind all nuts, graham cracker crumbs, cinnamon, and 1/3 cup sugar in processor. Using electric mixer, beat egg yolks, vanilla, 1/3 cup sugar, and remaining 1 tablespoon orange peel in large bowl until very thick, about 4 minutes. Using clean beaters, beat whites and salt in another large bowl to soft peaks. Gradually add 1 cup sugar; beat until stiff but not dry. Fold whites into yolk mixture, then fold in nut mixture. Transfer batter to prepared pan.
Bake cake until knife inserted into center comes out clean, about 50 minutes. Spoon cold syrup over hot cake. Cool completely. Cover; let stand up to 1 day. Cut into squares or diamonds.