While this cake tastes delicious on its own, enhance it with dollops of whipped cream or nondairy topping and a few orange segments.
7 large egg whites
Position rack in center of oven and preheat to 350°F. Generously coat 12-cup bundt pan (preferably nonstick) with margarine. In processor finely grind pecans with Mandel Cuts, 1/2 cup sugar, potato starch and cinnamon.
Beat egg whites and salt in large bowl until soft peaks form. Gradually add 1 cup sugar and beat until stiff but not dry. Beat yolks, orange peel, orange juice concentrate and remaining 1/2 cup sugar in medium bowl until just blended, about 1 minute. Mix in 1/4 cup melted margarine. Fold yolk mixture into whites in 3 additions. Fold in pecan mixture in 3 additions. Pour batter into prepared bundt pan.
Bake until tester inserted into center of cake comes out dry, about 50 minutes. Cool cake in pan on rack 20 minutes. Turn cake out onto rack and cool completely. (Can be made 2 days ahead. Cover cake tightly and store at room temperature.)
Cut cake into wedges. Garnish with orange segments and whipped cream, if desired, and serve.