Preheat oven to 350°F. Brush 13x9x2-inch metal baking pan with oil. Combine walnuts, almonds, and cake meal in processor; grind nuts finely. Using electric mixer, beat egg yolks, lemon peel, orange peel, cinnamon, and salt in large bowl until beginning to thicken, about 3 minutes. Gradually add 1/2 cup sugar, beating until very thick and light in color, about 2 minutes longer. Beat in orange juice; fold in nut mixture. Using clean dry beaters, beat egg whites in another large bowl until soft peaks form. Gradually add remaining 1/2 cup sugar, beating until stiff but not dry. Fold egg whites into yolk mixture in 3 additions. Transfer batter to prepared pan. Bake cake until puffed and deep golden and tester inserted into center comes out clean, about 35 minutes. Cool cake in pan on rack (center of cake will fall). Place large sieve over bowl. Cut off all peel and pith from oranges. Working over sieve, cut oranges between membranes to release segments into sieve. Squeeze any juice from orange membranes over. Let oranges drain while preparing syrup. Bring pomegranate juice, sugar, lemon juice, and reserved orange peel to boil in medium saucepan over medium-high heat, stirring until sugar dissolves and thin syrup forms. Remove from heat. Holding orange peel back with spoon, pour 3/4 cup syrup into small bowl. Spoon over cake; let stand at least 1 hour. Add drained orange juice to remaining syrup in pan. Boil syrup with peel until reduced enough to coat spoon, about 8 minutes. Discard peel. DO AHEAD Cake can be made 1 day ahead. Cover and let stand at room temperature. Place orange segments in bowl. Cover and refrigerate orange segments and syrup separately. Add syrup to orange segments; let compote stand 15 minutes. Trim edges of cake. Cut cake lengthwise into 2 1/2-inch-wide strips. Cut strips on diagonal into diamonds; place on plates. Spoon compote over and serve.