For the Cake: Preheat oven to 350°F (180°C, Gas Mark 4). Grease and flour 2 (9-in/23 cm) round cake pans. Sift flour, cocoa powder, baking soda and salt. Set aside. Beat butter and granulated sugar in large bowl with electric mixer on medium speed 5 minutes or until light and fluffy. Beat in eggs, 1 at a time. Mix in sour cream, milk, food color and vanilla. Gradually beat in flour mixture on low speed until just blended. Do not over beat. Pour batter into prepared pans. Bake 35 to 40 minutes or until toothpick inserted in center comes out clean. Cool in pan 10 minutes. Remove from pans; cool completely on wire rack.
For the Frosting: Beat cream cheese butter sour cream and vanilla in large bowl until light and fluffy. Gradually beat in icing sugar until smooth. Fill and frost cooled cake with frosting.