PREHEAT oven to 350 degrees.
COMBINE eggs, 1/4 cup sour cream and vanilla. Set aside. Mix together dry ingredients and orange zest in large bowl. Add butter and remaining sour cream. Mix on low speed until moistened. Beat on medium speed until creamy. Gradually add egg mixture in thirds, mixing well after each addition. Spread batter in prepared 9-cup fluted tube pan. Bake until tester inserted in center comes out clean, 55 to 65 minutes.
REMOVE cake from oven. Poke holes in top of cake. Brush with 1/2 of Grand Marnier Syrup. Cool in pan 10 minutes. Invert onto cooling rack. Brush with remaining syrup. Cool before glazing with Chocolate Ganache.
TIP: Process toasted almonds with sugar and orange zest in a food processor for perfect texture.
GRAND MARNIER SYRUP: Heat sugar, orange juice and Grand Marnier in small saucepan until dissolved. (note: For non-alcoholic version, replace with additional orange juice.)
CHOCOLATE GANACHE GLAZE: Process in food processor or grate until very fine. Scald cream in small saucepan. Add grated chocolate. Cover and let sit for five minutes. Gently stir until smooth. If necessary, stir on low heat to melt chocolate. Place cake on cooling rack with waxed paper underneath to catch drippings. Pour ganache glaze over cake